我检查后，你原来的总体思路是对的：关 WiFi、降 CPU、降亮度、低频电量轮询、自适应 delay，都是适合 Cardputer BLE 遥控器的省电方向。真正需要修的是几个“容易误省电/实际没生效”的点：

1. BLE 发射功率写法要改：新版 NimBLE 的 NimBLEDevice::setPower() 参数是 dBm 数值，不是 esp_power_level_t 枚举；而 Espressif 的 ESP_PWR_LVL_N3 是 BLE TX power level 枚举，对应 -3 dBm。混用时可能达不到你注释里写的效果。(h2zero.github.io)
2. 建议强制使用 NimBLE 模式：ESP32-BLE-Keyboard 文档说明 NimBLE 模式能显著降低 RAM/Flash 占用，并且支持 setBatteryLevel()；你代码里又直接使用了 NimBLEDevice，所以应明确 #define USE_NIMBLE。(GitHub)
3. 不要随便上 deep sleep / 手动 light sleep：ESP-IDF 文档明确说 Light-sleep / Deep-sleep 下 Wi-Fi/Bluetooth 连接不会保持；如果要保持 BLE 连接，需要更复杂的 Bluetooth modem-sleep + automatic light-sleep 配置，不适合直接塞进 Arduino 版 BLE HID 遥控器里。(Espressif Systems)
4. 可在 M5 初始化时禁用未用硬件：M5Unified 的 M5.config() 默认有 internal_mic、internal_spk、internal_imu 等开关；你的遥控器不用麦克风、扬声器、IMU，建议初始化时关闭。(M5Stack Documentation)
5. 屏幕省电方向正确：M5GFX/M5Stack 文档也说明背光亮度会直接影响电池消耗；sleep()/wakeup() 与背光是两个层面，保守做法是默认只关背光，必要时再打开 LCD sleep。(GitHub)

下面是我整理后的可直接替换版。保留你的原功能，新增了 Fn+L 切换屏幕亮度档位，并把实际电量同步到 BLE HID 电池服务。

cpp
/*
  DX1 II Bluetooth Remote for M5Stack Cardputer-Adv
  Power-optimized revision

  Main changes:
  1. Force ESP32-BLE-Keyboard to use NimBLE mode.
  2. Fix BLE TX power setting: use dBm value for NimBLEDevice::setPower().
  3. Disable unused M5 internal peripherals: speaker, mic, IMU.
  4. Keep WiFi fully off.
  5. Lower default brightness and add Fn+L brightness presets.
  6. Report real battery level to BLE HID Battery Service.
  7. Use longer battery polling while screen is off.
  8. Wake screen on any key press, but only redraw when needed.
*/

#define USE_NIMBLE

#include <M5Cardputer.h>

// --- 在引入 BleKeyboard 之前，取消所有冲突的宏定义 ---
#undef KEY_LEFT_CTRL
#undef KEY_LEFT_SHIFT
#undef KEY_LEFT_ALT
#undef KEY_BACKSPACE
#undef KEY_TAB
#undef KEY_DELETE
#undef KEY_F1
#undef KEY_F2
#undef KEY_F3
#undef KEY_F4
#undef KEY_F5
#undef KEY_F6
#undef KEY_F7
#undef KEY_F8
#undef KEY_F9
#undef KEY_F10
#undef KEY_F11
#undef KEY_F12

#include <BleKeyboard.h>
#include <Preferences.h>
#include <NimBLEDevice.h>
#include <WiFi.h>
#include <esp_wifi.h>

BleKeyboard bleKeyboard("DX1II Remote", "M5Stack", 100);
Preferences prefs;

struct KeyAction {
  char key;
  char sendChar;
  const char* label;
};

struct MediaAction {
  char key;
  const uint8_t* mediaKey;
  const char* label;
};

// Keep these in sync with dx1_bridge's HOTKEY_ACTIONS map.
static const KeyAction kActions[] = {
  {'c', 'c', "连接"},
  {'x', 'x', "断开"},
  {'1', '1', "音量-"},
  {'2', '2', "音量+"},
  {'m', 'm', "静音切换"},
  {'i', 'i', "输入切换"},
  {'o', 'o', "输出切换"},
};
static const size_t kActionCount = sizeof(kActions) / sizeof(kActions[0]);

static const MediaAction kMediaActions[] = {
  {'p', KEY_MEDIA_PLAY_PAUSE, "播放/暂停"},
  {'n', KEY_MEDIA_NEXT_TRACK, "下一曲"},
  {'b', KEY_MEDIA_PREVIOUS_TRACK, "上一曲"},
};
static const size_t kMediaActionCount = sizeof(kMediaActions) / sizeof(kMediaActions[0]);

// Auto screen-off timeout presets, in seconds. Cycle with Fn+, / Fn+.
static const uint16_t kSleepPresetsSec[] = {10, 30, 60, 120, 300};
static const size_t kSleepPresetCount = sizeof(kSleepPresetsSec) / sizeof(kSleepPresetsSec[0]);

// 新增：亮度档位。默认使用 45，续航优先；需要更亮可 Fn+L 切换。
static const uint8_t kBrightnessPresets[] = {25, 45, 70, 100};
static const size_t kBrightnessPresetCount = sizeof(kBrightnessPresets) / sizeof(kBrightnessPresets[0]);

static bool autoSleepEnabled = true;
static uint8_t sleepPresetIndex = 1;
static uint8_t brightnessPresetIndex = 1;
static bool screenOff = false;
static unsigned long lastActivityMs = 0;

// 如果你实测 Display.sleep()/wakeup() 稳定，可改成 true 进一步降低屏幕控制器功耗。
// 默认 false：只关背光，稳定性最好。
static const bool kUseDisplaySleep = false;

// 0 = status page, 1 = key legend page
static uint8_t currentPage = 0;

static String lastActionText = "等待按键...";
static bool lastConnectedState = false;
static String peerAddressText = "";

// ESP32-S3 降频到 80 MHz。继续降低到 40 MHz 可能影响 BLE/I2C/SPI 响应。
static const uint32_t kCpuFrequencyMhz = 80;

// NimBLEDevice::setPower() 使用 dBm 数值，不使用 ESP_PWR_LVL_N3 枚举。
static const int8_t kBleTxPowerDbm = -3;

// Battery state
static int32_t batteryLevel = -1;
static bool batteryCharging = false;
static unsigned long lastBatteryPollMs = 0;

// 亮屏时 30 秒；熄屏时 120 秒。熄屏时电量显示不可见，没有必要频繁读取。
static const unsigned long kBatteryPollAwakeMs = 30000;
static const unsigned long kBatteryPollScreenOffMs = 120000;

// 自适应 loop 延时。熄屏时适当放慢，但不要太大，避免键盘 FIFO 在连续按键时堆积。
static const uint16_t kLoopDelayConnectedMs = 8;
static const uint16_t kLoopDelayDisconnectedMs = 15;
static const uint16_t kLoopDelayScreenOffConnectedMs = 18;
static const uint16_t kLoopDelayScreenOffDisconnectedMs = 30;

uint8_t currentBrightness() {
  if (brightnessPresetIndex >= kBrightnessPresetCount) {
    brightnessPresetIndex = 1;
  }
  return kBrightnessPresets[brightnessPresetIndex];
}

void applyPowerSavingConfigBeforeBle() {
  // 本固件不使用 WiFi。disconnect + WIFI_OFF + esp_wifi_stop 都执行，忽略未初始化时的返回错误。
  WiFi.disconnect(true, true);
  WiFi.mode(WIFI_OFF);
  esp_wifi_stop();

  // 降低 CPU 频率。
  setCpuFrequencyMhz(kCpuFrequencyMhz);
}

void applyPowerSavingConfigAfterBleBegin() {
  // NimBLE 当前 API 使用 dBm 数值。-3 dBm 适合近距离桌面遥控。
  // 若连接不稳，改成 0 或 3。
  NimBLEDevice::setPower(kBleTxPowerDbm);
}

uint16_t getLoopDelayMs(bool connected) {
  if (screenOff) {
    return connected ? kLoopDelayScreenOffConnectedMs : kLoopDelayScreenOffDisconnectedMs;
  }
  return connected ? kLoopDelayConnectedMs : kLoopDelayDisconnectedMs;
}

unsigned long getBatteryPollIntervalMs() {
  return screenOff ? kBatteryPollScreenOffMs : kBatteryPollAwakeMs;
}

void pushBleBatteryLevel() {
  if (batteryLevel < 0) return;

  uint8_t level = (uint8_t)constrain((int)batteryLevel, 0, 100);
  bleKeyboard.setBatteryLevel(level);
}

void updatePeerAddress() {
  peerAddressText = "";

  NimBLEServer* server = NimBLEDevice::getServer();
  if (!server || server->getConnectedCount() == 0) return;

  NimBLEConnInfo info = server->getPeerInfo(0);
  peerAddressText = String(info.getAddress().toString().c_str());
}

bool refreshBatteryStatus() {
  int32_t level = M5Cardputer.Power.getBatteryLevel();
  int8_t chg = M5Cardputer.Power.isCharging();
  bool charging = (chg == 1);

  if (level >= 0) {
    level = constrain((int)level, 0, 100);
  }

  bool changed = (level != batteryLevel) || (charging != batteryCharging);
  batteryLevel = level;
  batteryCharging = charging;

  if (changed) {
    pushBleBatteryLevel();
  }

  return changed;
}

void drawBatteryIcon(int xRight, int y, int level, bool charging) {
  auto &lcd = M5Cardputer.Display;
  const int w = 22, h = 11, nub = 4;
  const int x = xRight - w - 3;

  const uint16_t frameColor = 0xC618;

  lcd.drawRect(x, y, w, h, frameColor);
  lcd.fillRect(x + w, y + (h - nub) / 2, 2, nub, frameColor);
  lcd.fillRect(x + 2, y + 2, w - 4, h - 4, BLACK);

  if (level < 0) {
    lcd.setFont(&fonts::efontCN_12);
    lcd.setTextColor(0x7BEF, BLACK);
    lcd.setCursor(x + w / 2 - 3, y - 1);
    lcd.print("?");
    return;
  }

  uint16_t fillColor;
  if (level <= 15) {
    fillColor = RED;
  } else if (level <= 40) {
    fillColor = YELLOW;
  } else {
    fillColor = GREEN;
  }

  int innerW = w - 4;
  int fillW = (innerW * level) / 100;
  if (fillW > 0) {
    lcd.fillRect(x + 2, y + 2, fillW, h - 4, fillColor);
  }

  if (charging) {
    lcd.setFont(&fonts::efontCN_12);
    lcd.setTextColor(YELLOW, BLACK);
    lcd.setCursor(x - 12, y - 1);
    lcd.print("+");
  }
}

void wakeScreen() {
  if (!screenOff) return;

  screenOff = false;

  if (kUseDisplaySleep) {
    M5Cardputer.Display.wakeup();
  }

  M5Cardputer.Display.setBrightness(currentBrightness());
}

void turnScreenOff() {
  if (screenOff) return;

  screenOff = true;
  M5Cardputer.Display.setBrightness(0);

  if (kUseDisplaySleep) {
    M5Cardputer.Display.sleep();
  }
}

void drawStatusPage() {
  auto &lcd = M5Cardputer.Display;
  int y = 2;

  lcd.setFont(&fonts::efontCN_16);
  lcd.setTextColor(WHITE, BLACK);
  lcd.setCursor(4, y);
  lcd.print("DX1 II 蓝牙遥控");

  drawBatteryIcon(lcd.width() - 4, y + 2, batteryLevel, batteryCharging);

  y += 20;

  lcd.setFont(&fonts::efontCN_14);
  bool connected = bleKeyboard.isConnected();

  lcd.setTextColor(connected ? GREEN : RED, BLACK);
  lcd.setCursor(4, y);
  lcd.print(connected ? "蓝牙: 已连接" : "蓝牙: 等待PC连接...");

  lcd.setTextColor(0xC618, BLACK);
  char battText[24];
  if (batteryLevel < 0) {
    snprintf(battText, sizeof(battText), "电量: --");
  } else {
    snprintf(battText, sizeof(battText), "电量: %ld%%%s",
             (long)batteryLevel, batteryCharging ? " 充电中" : "");
  }

  int battTextW = lcd.textWidth(battText);
  lcd.setCursor(lcd.width() - battTextW - 4, y);
  lcd.print(battText);

  y += 17;

  lcd.setTextColor(0xC618, BLACK);
  lcd.setCursor(4, y);

  if (connected && peerAddressText.length() > 0) {
    lcd.print("设备地址: " + peerAddressText);
  } else {
    lcd.print("设备地址: -");
  }

  y += 17;

  lcd.setCursor(4, y);
  lcd.printf("自动熄屏: %s (%us)",
             autoSleepEnabled ? "开" : "关",
             kSleepPresetsSec[sleepPresetIndex]);

  y += 17;

  lcd.setCursor(4, y);
  lcd.printf("亮度: %u / 100", currentBrightness());

  y += 20;

  lcd.drawFastHLine(0, y, lcd.width(), 0x39C7);
  y += 6;

  if (batteryLevel >= 0 && batteryLevel <= 15 && !batteryCharging) {
    lcd.setTextColor(RED, BLACK);
    lcd.setCursor(4, y);
    lcd.print("低电量，请尽快充电");
    y += 16;
  }

  lcd.setTextColor(YELLOW, BLACK);
  lcd.setCursor(4, y);
  lcd.print(lastActionText);

  lcd.setTextColor(0x7BEF, BLACK);
  lcd.setCursor(4, lcd.height() - 16);
  lcd.print("Fn+/ 说明  Fn+L 亮度");
}

void drawLegendPage() {
  auto &lcd = M5Cardputer.Display;
  const int colX[2] = {4, 128};
  int y = 2;

  lcd.setFont(&fonts::efontCN_14);
  lcd.setTextColor(WHITE, BLACK);
  lcd.setCursor(4, y);
  lcd.print("按键说明 (Fn+/ 返回)");

  drawBatteryIcon(lcd.width() - 4, y + 2, batteryLevel, batteryCharging);

  y += 20;

  lcd.setFont(&fonts::efontCN_12);
  lcd.setTextColor(0xC618, BLACK);

  const char* rows[7][2] = {
    {"C 连接", "X 断开"},
    {"1 音量-", "2 音量+"},
    {"M 静音", "I 输入"},
    {"O 输出", "P 播放暂停"},
    {"N 下一曲", "B 上一曲"},
    {"Fn+S 熄屏开关", "Fn+,/. 熄屏时长"},
    {"Fn+L 亮度档位", "Fn+/ 页面切换"},
  };

  for (int row = 0; row < 7; row++) {
    lcd.setCursor(colX[0], y);
    lcd.print(rows[row][0]);

    lcd.setCursor(colX[1], y);
    lcd.print(rows[row][1]);

    y += 15;
  }
}

void drawUI() {
  if (screenOff) return;

  auto &lcd = M5Cardputer.Display;

  lcd.startWrite();
  lcd.fillScreen(BLACK);
  lcd.setTextSize(1);

  if (currentPage == 0) {
    drawStatusPage();
  } else {
    drawLegendPage();
  }

  lcd.endWrite();
}

void sendComboKey(char c) {
  bleKeyboard.press(KEY_LEFT_CTRL);
  bleKeyboard.press(KEY_LEFT_ALT);
  bleKeyboard.press(c);

  // 保留短延时，保证主机端稳定识别组合键。
  delay(15);

  bleKeyboard.releaseAll();
}

bool handleDx1Key(char c) {
  if (c >= 'A' && c <= 'Z') {
    c = c - 'A' + 'a';
  }

  for (size_t i = 0; i < kActionCount; i++) {
    if (c != kActions[i].key) continue;

    if (!bleKeyboard.isConnected()) {
      lastActionText = "未连接蓝牙, 无法发送";
    } else {
      sendComboKey(kActions[i].sendChar);
      lastActionText = String("已发送: ") + kActions[i].label;
    }

    return true;
  }

  return false;
}

bool handleMediaKey(char c) {
  if (c >= 'A' && c <= 'Z') {
    c = c - 'A' + 'a';
  }

  for (size_t i = 0; i < kMediaActionCount; i++) {
    if (c != kMediaActions[i].key) continue;

    if (!bleKeyboard.isConnected()) {
      lastActionText = "未连接蓝牙, 无法发送";
    } else {
      bleKeyboard.write(kMediaActions[i].mediaKey);
      lastActionText = String("媒体: ") + kMediaActions[i].label;
    }

    return true;
  }

  return false;
}

bool handleSettingsKey(char c) {
  if (c >= 'A' && c <= 'Z') {
    c = c - 'A' + 'a';
  }

  if (c == 's') {
    autoSleepEnabled = !autoSleepEnabled;
    prefs.putBool("autoSleep", autoSleepEnabled);

    lastActionText = autoSleepEnabled ? "自动熄屏: 开" : "自动熄屏: 关";
    return true;
  }

  if (c == ',') {
    sleepPresetIndex = (sleepPresetIndex == 0)
                         ? (kSleepPresetCount - 1)
                         : (sleepPresetIndex - 1);

    prefs.putUChar("sleepIdx", sleepPresetIndex);
    lastActionText = String("熄屏时间: ") + kSleepPresetsSec[sleepPresetIndex] + "s";
    return true;
  }

  if (c == '.') {
    sleepPresetIndex = (sleepPresetIndex + 1) % kSleepPresetCount;

    prefs.putUChar("sleepIdx", sleepPresetIndex);
    lastActionText = String("熄屏时间: ") + kSleepPresetsSec[sleepPresetIndex] + "s";
    return true;
  }

  if (c == '/') {
    currentPage = currentPage == 0 ? 1 : 0;
    lastActionText = currentPage == 0 ? "已切换到状态页" : "已切换到按键说明页";
    return true;
  }

  if (c == 'l') {
    brightnessPresetIndex = (brightnessPresetIndex + 1) % kBrightnessPresetCount;
    prefs.putUChar("brightIdx", brightnessPresetIndex);

    if (!screenOff) {
      M5Cardputer.Display.setBrightness(currentBrightness());
    }

    lastActionText = String("屏幕亮度: ") + currentBrightness();
    return true;
  }

  return false;
}

/*
  Cardputer-Adv / newer M5Cardputer Fn-layer fix:
  不依赖 status.word 判断 Fn+/、Fn+,、Fn+.。
*/
bool handleFnSettingsPhysical() {
  if (!M5Cardputer.Keyboard.isKeyPressed(KEY_FN)) {
    return false;
  }

  if (M5Cardputer.Keyboard.isKeyPressed('s') ||
      M5Cardputer.Keyboard.isKeyPressed('S')) {
    return handleSettingsKey('s');
  }

  if (M5Cardputer.Keyboard.isKeyPressed(',')) {
    return handleSettingsKey(',');
  }

  if (M5Cardputer.Keyboard.isKeyPressed('.')) {
    return handleSettingsKey('.');
  }

  if (M5Cardputer.Keyboard.isKeyPressed('/')) {
    return handleSettingsKey('/');
  }

  if (M5Cardputer.Keyboard.isKeyPressed('l') ||
      M5Cardputer.Keyboard.isKeyPressed('L')) {
    return handleSettingsKey('l');
  }

  return false;
}

void setup() {
  auto cfg = M5.config();

  // 省电：不用的内部硬件直接不初始化。
  cfg.internal_spk = false;
  cfg.internal_mic = false;
  cfg.internal_imu = false;
  cfg.external_speaker_value = 0;
  cfg.external_display_value = 0;
  cfg.led_brightness = 0;

  M5Cardputer.begin(cfg, true);
  M5Cardputer.Display.setRotation(1);

  prefs.begin("dx1remote", false);
  autoSleepEnabled = prefs.getBool("autoSleep", true);
  sleepPresetIndex = prefs.getUChar("sleepIdx", 1);
  brightnessPresetIndex = prefs.getUChar("brightIdx", 1);

  if (sleepPresetIndex >= kSleepPresetCount) {
    sleepPresetIndex = 1;
  }

  if (brightnessPresetIndex >= kBrightnessPresetCount) {
    brightnessPresetIndex = 1;
  }

  M5Cardputer.Display.setBrightness(currentBrightness());

  // 双保险：即使库内部默认初始化过，也主动关闭不用的音频任务。
  M5Cardputer.Speaker.end();
  M5Cardputer.Mic.end();

  applyPowerSavingConfigBeforeBle();

  bleKeyboard.begin();
  applyPowerSavingConfigAfterBleBegin();

  refreshBatteryStatus();
  pushBleBatteryLevel();
  lastBatteryPollMs = millis();

  lastActivityMs = millis();
  drawUI();
}

void loop() {
  M5Cardputer.update();

  unsigned long now = millis();
  bool connected = bleKeyboard.isConnected();

  if (connected != lastConnectedState) {
    lastConnectedState = connected;

    if (connected) {
      delay(150);
      applyPowerSavingConfigAfterBleBegin();
      updatePeerAddress();
      pushBleBatteryLevel();
      lastActionText = "蓝牙已连接";
    } else {
      peerAddressText = "";
      lastActionText = "蓝牙已断开";
    }

    wakeScreen();
    lastActivityMs = millis();
    drawUI();
  }

  // 电量低频轮询；变化会同步 BLE HID 电池服务，但不会主动唤醒屏幕。
  if (now - lastBatteryPollMs >= getBatteryPollIntervalMs()) {
    lastBatteryPollMs = now;

    if (refreshBatteryStatus() && !screenOff) {
      drawUI();
    }
  }

  if (M5Cardputer.Keyboard.isChange() && M5Cardputer.Keyboard.isPressed()) {
    Keyboard_Class::KeysState status = M5Cardputer.Keyboard.keysState();
    bool handled = false;
    bool wasScreenOff = screenOff;

    // 任意按键先唤醒屏幕并刷新活动时间；无效键不发送蓝牙。
    wakeScreen();
    lastActivityMs = millis();

    if (M5Cardputer.Keyboard.isKeyPressed(KEY_FN) || status.fn) {
      handled = handleFnSettingsPhysical();
    } else {
      for (auto c : status.word) {
        if (handleDx1Key(c)) {
          handled = true;
          continue;
        }

        if (handleMediaKey(c)) {
          handled = true;
          continue;
        }
      }
    }

    // 熄屏状态下任意键唤醒后需要重绘；正常亮屏时只有处理过的键才重绘。
    if (handled || wasScreenOff) {
      drawUI();
    }
  }

  if (autoSleepEnabled && !screenOff) {
    unsigned long timeoutMs = (unsigned long)kSleepPresetsSec[sleepPresetIndex] * 1000UL;

    if (millis() - lastActivityMs >= timeoutMs) {
      turnScreenOff();
    }
  }

  delay(getLoopDelayMs(connected));
}

你还需要注意的两点

编译时建议确认 ESP32-BLE-Keyboard 真的启用了 NimBLE；上面代码已加 #define USE_NIMBLE，如果你用 PlatformIO，也可以在 platformio.ini 里加 -D USE_NIMBLE，这样更稳。ESP32-BLE-Keyboard 文档也明确把 NimBLE 作为低内存模式，并支持媒体键和电量上报。(GitHub)

kBleTxPowerDbm = -3 适合近距离。如果你发现 PC 端偶尔断连，优先改成 0；如果隔墙或距离较远，再改成 3。不要再写 ESP_PWR_LVL_N3 传给 NimBLEDevice::setPower()，因为当前 NimBLE 文档写的是 dBm 数值参数。(h2zero.github.io)