@guizzy I'm not the best person to answer this, seeing that I don't like those kind of sites in general. But with that caveat, I keep hearing two things about the existing sites:
(1) their communities seem to be full of negativity and anger (and whatever social / political point of view someone dislikes)
(2) their moderation seems to lack transparency and to tilt in one direction or another.

I'd like to think that federation can help, but at this point, I'd probably recommend finding something that works mostly peer-to-peer (lightly-moderated federation hubs would be okay, as long as the individual user could still block unwanted posters and obtain "fediblocked" posts via p2p if desired).

I'll skip the bonus question, for obvious reasons.