I’m very sorry that I’ve overseen your q here. And its a good q!
(also answers @Bristow s q)
The diff is that UNOFFIFIAL is pure /e/ untouched while CUSTOM have some apps added (including a patched google play store) . That should been mentioned in the XDA thread but the whole project was in the transition to become official …which then failed and I forgot about to transfer the descriptions back and add notes for the current state. Sorry for the confusion here. Will be fixed asap!
Note: The play store is able to use the microG backend including the use of paid apps. It can be simply disabled if not needed!
The list of apps added: automation_scripts/main.yml at ansible · sfX-android/automation_scripts · GitHub (phonesky is the patched play store)