I've been thinking of watching the BanG Dream anime. Is it gud?
It focuses entirely on popipa, with only bit appearances by the other bands. I thought it started off pretty cute, but then Twinkle Twinkle Little Star hits, and the show never really won me back.
It's worth noting that [I'm pretty sure] Chata Maru has gone into more detail about Marisa and Alice's marriage in the MariAli ga Kosodate series. That particular doujin just hasn't been scanlated. In fact, there are a bunch of manga in the series that haven't been translated.