Firefox + Betterfox + UBO vs Brave out of the box

You’ll be fine, no matter what. In theory, I think with enough tweaking, you can apparently get Firefox somewhat close to Mullvad levels of protection, but depending on what your threat model, how you want your web experience to be, it’s probably not necessary. But I do want to say, Betterfox is not recommended. You’re going to need Arkenfox for this.