The communities on different instances are not the same. You can subscribe to both. The idea behind federation is that one company/server can't control all the traffic. It might result in a little splintering of communities, but I think it's ultimately better to be decentralized.
That is one that I haven't done yet, but I've found this guide to be a good outline.
It's still in the works, but I'm planning on:
It's definitely a lot of stuff, but I'm trying to reduce my reliance on cloud services. Really excited to get this stuff going.
You can download Thunder from IzzyOnDroid (you can add this as a repository to F-Droid).
It's easy enough to install LineageOS on OnePlus phones. Would rather do that than deal with shady stuff like this.
Faceit anticheat is very intrusive and requires disabling virtualization in bios. Also means no Linux support.