Back with newsgroups the general rule was to go from general to specific. You start with a general discussion group and when discussions about video games get annoying you create a games group. If then there are too many Baldur’s Gate discussions you create BG. If they are dominated by Baldur’s Gate 3 you create a Baldur’s Gate 3 group. If everyone is fawning over Withers you create a Withers group which of course will be flooded with discussion about the Withers’ tits mod, which shall get its own group.

Meaning you should create a group when demand is there and not the other way around.