I didnt make any changes for any countries. I left everything default. There were a lot of countries i couldn’t opt into because my app is rated mature. No its not a nasty app, just kinda closer in content to like grand theft auto. Haha.
As for setting up in ios and android, all of the tuts ive been through said its supposed to be the same app ID. But im not a great source of truth because im only developing for android right now.