I had used Firefox+uBO on desktop for many years, have used Brave afterwards (desktop and mobile) and Brave’s adblocker blocks ads about as good as uBO. Just if you want to do dynamic filtering, like medium mode, uBO still has more features. What Brave’s ad blocker does better is dealing with cookie banners.
Brave does not use uBO under the hood, but supports uBO syntax. The really nice part about Brave’s ad blocker is that it uses the networking stack directly and is written in Rust, which circumvents the security shortcomings of the mv2 extension system.
There is no way for you to know based on visiting a test site. People should really stop using these fingerprinting websites. But yeah, since it is a really seldomly browser with barely any mitigations it’s not great in terms of fingerprinting and you could even end up being unique depending on your configuration.