I recommend Brave when you need a Chromium-based browser. In the Chromium world you will not find anything better than Brave.
Of course, I do not recommend to use Brave as a primary browser... just for these cases when something doesn't work in hardened Firefox ESR. I stress on hardened, because regular out of the box Firefox is simply not enough. And I stress on the ESR version of Firefox, since it's an enterprise-grade browser which (once hardened) will serve you well for at least 9 months.
TBH, I am sad that Brave didn't go without its own controversies and bloat. Still, it remains the only Chromium-based browser that de-Googles soooooo much cr#p in the Chromium code so that you can browse with peace of mind.
Vivaldi is definitely a no-go for me, since it's not open source. Period. Whatever their marketing department says, being closed source is a red flag. Why? Because they can inject shady stuff even in the UI! "We are not fully open source because someone will steal our work"... hilarious. I bet that's exactly the same reason why Chome is not open source! Somebody is going to steal Google's work (irony & laughter).
Probably indeed Vivaldi is safe to use with some settings disabled, but if such a critical piece of software like a browser is not open source, then nobody can verify if some UI elements (like settings) really do anything or not. This problem is especially true for Android (iPhone is waaaay worse) where Google Firebase is lurking everywhere, even when you "disable" some settings in a given app. The only way to be safe there is to use something like Proton VPN or some DNS-based blocklists (they carry their own privacy risk with them tho...) to nuke Firebase on a device level.
Actually... this is the only internet privacy company that I trust. I just hope that they start to deliver new products and apps faster... especially on Android, so that we can de-Google our lives as much as possible.