Jitsi is not P2P for group conversations - all streams are multiplexed by the server (the videobridge).

100% agreed about spotty connections, it does not handle them very well. As long as everyone has a decent connection and enough CPU, it handles groups of 10+ participants just fine. My company ended up switching to Google Meet for reliability reasons, but was a year ago so it might be better now.

Yeah, it's a shame, had to install the Chromium snap only for this (Ubuntu 19.10). But then it did work very well (don't forget to enable the "record and play sound" permission for the snap.)

Yes, admins can mute and kick. And if you allow anonymous channel creation, the first to enter a channel automatically has admin right. I don't know if kicked participants (especially unauthenticated) can re-join at once, after a delay or any other rule.