Brave does an enormous about of non-browser "stuff." Video calls, offline playlists, customizable news feeds, crypto wallet... they are trying to build a "super app" rather than a browser. The idea is that you can trust them because they aren't FAANG, but the problem is that if they actually were to succeed then they would be FAANG.

I haven't used Firefox in ages but AFAIK it has very little bloatware. The problem, from the perspective of a web dev, is that it has quite a few rendering quirks/bugs. These days chromium sets the standard for the "correct" way to render things.