BiTGApps is a custom version of gapps package. It is a minimal sized package. BiTGApps packages for supported Android Versions does not go beyond 90MB in size. It is an optimized gapps package. i.e; It comes with optimized APKs, Battery optimization for all system installed gapps and other system services optimization.
This minimal gapps package has all the bare minimum google applications to get Google Services functionality. You need to perform clean flash installation if your previous installed gapps package is OpenGApps or any other like MindTheGApps, NikGApps, Weeb GApps, etc. Updates are weekly or after a week. Addon package functionality is also given for installing additional apps like Google Assistant only.
There is no other addon package available. What packages (APKs) included in BiTGApps mentioned in every specific XDA post prior to Android Version and Android Arch. Also check XDA Post for installation instruction. Allow-in-powersave or so called Battery Optimization for gapps is broken in Pie ROMs and it is described in Android 9 XDA post already. Please check Guide To Optimize GApps in Pie ROMs section.
It is the only exception in Pie ROMs and doesn’t require anything like that in android version below 9 or above.
