Firefox’s free VPN will offer 50 gigabytes of monthly data, which is pretty generous for a browser-based VPN. A Mozilla account is required to make use of it, which isn’t a hardship (they’re free), but is a point of friction some may wish to know upfront.
I definitely wouldn’t call “local llm features” dangerous.
Edit: I suppose the tab grouping may not be local? Their docs don’t really specify one way or another. So I could be wrong in that one. The rest is definitely local, minus the “you have to sign in with an llm account” sidebar chat thing.