Ultimately, Brave Browser is the apparatus of an advertising company, a bloated and complicated experience for the average user, and the pet project of the person kicked out of Mozilla for continuing to defend harmful political donations. If you want a privacy-focused web browser, use Firefox or Vivaldi. If you want to support your favorite content creators and publishers, turn on advertisements or support them through the methods they already support (Patreon, Ko-Fi, and so on). Brave Browser is irredeemable, and you should not use it under any circumstances.
I don't use brave and I am not interested in using it, so YMMV.
Not according to PrivacyTests.org. It lacks a lot of state partitioning, amongst other things. Just FYI, the front end UI is closed source, but the backend/engine is open source, because they're just another chromium spin off.