Is having both a normal social media account & a federated version okay ? I've seen a lot of people delete their Twitter and then hop on Mastodon because they're worried about Musk. Whether their concern about Musk is valid is another question. How do people see his acquisition of Twitter as a bad thing? If anything he will try to improve it no?
Similarly I find the Fediverse interesting technically and there's at least some content I enjoy, so I have that too.
It's the same with Discord and Matrix. It's probably even better to have both accounts because then it isn't as much of a hurdle to move platforms if one thing doesn't go in the direction you'd like.
As for people leaving Twitter over Musk, I expect most of the big ones to quietly come back once they find an excuse, after all, most of them are mainly addicted to the attention, which isn't as easy to earn in the Fediverse due to a lack of a recommender system with perverse incentives to manipulate.