Battery drainage is Android Pie issue itself. even pixel's are under heat. |
Gcam is not officially available for any device other then pixel and Nexus devices. All available apks are just modded apps by different developers. In no way Xiaomi developers can do anything about them. None of the pixel 3 apks are stable yet for Android Pie on any device. So wait for GCam mod apk developers to work and fix it.