As it stands, here's what I've gathered from this discussion and my own testing:
Using a VPN or TorVPN to route traffic, one can use Vanadium with Javascript disabled to block fingerprint tracking and tracking via IP. Vanadium also makes cookie tracking difficult due to state partition and site isolation. This is the most secure option. One can change timezone in settings to UTC for more privacy.
Tor Browser with the Safest setting is going to be the most anonymous option, however Firefox Android has no sandboxing and it seems Tor Browser uses an embedded binary similar to Orbot. Orbot has various performance and security issues that users have brought concerns up over.
Brave makes little difference in privacy, and is not as secure.
Ironfox's implementation of Fission doesn't seem production-ready on Android, and I wouldn't trust the security of it. Also the GOS account brought up that it might not be a real sandbox, contrary to how Mozilla frames the feature. I'd trust GOS over Mozilla any day though personally.
TLDR: Use Vanadium with VPN or TorVPN for security, Tor Browser for anonymity.