As far as I understand, you kinda choose better security using Chromium or better privacy using Firefox with addons/forks

Lot of ressources say Brave is trash compared to Ungoogled, but Brave still adds stuff

Complicated, GrapheneOS recommends Vanadium or at least Brave on mobile

As I would trust GrapheneOS for doing a insane job based on Android, if they make their "own" version of Chromium, I don't have much doubts that they know what they talking about on Chromium/Firefox.

Also looking at their forum, they answer lot of questions I can barely understand

Seen in times to times saying the service and company is way more important