This means putting your trust in Obscura, since they’re the 1st hop, receiving your data without additional encryption, a new player, who yet has to prove that they’re trustworthy.

I’ve not checked but the whole claim is to use additional encryption, between you and the 2nd hop.

With our 2-party setup, Obscura operates the 1st hop, and we’re proud to partner with Mullvad who operates the 2nd (exit) hop. As the WireGuard packets are end-to-end encrypted to Mullvad’s servers, we never see any parts of your packet in plaintext (not even SNI). In fact, you can check your connected server’s public key in the Obscura App against those listed on Mullvad’s server page!

https://obscura.net/blog/bootstrapping-trust/#obscura

It’s better to avoid re-encoding as it lose quality.

Sadly Firefox has no tab sandboxing on mobile so yeah, it is less secure.

And while I agree the Brave company is shady, the browser has good security features.