They're disabled by default. It's better to try it out than to read opinions on the internet about the browser and form a viewpoint, I say this because I too have been guilty of the same.
Quick Google result: https://github.com/brave/brave-browser/issues/5429
The GitHub issues that you linked also are closed. I followed the duplicates and they're all closed with comments mentioning that it's been fixed.
The ads and crypto stuff are also not exactly as simple to opt out as "literally disable it in the welcome screen when you first install" as one commenter enthusiastically mentioned.
All of it is definitely opt-in. Even Brave Rewards are disabled by default.