You need to know that the Tor Browser disables a lot of stuff that Firefox has to lower the attack surface, and you can lock it down further using the Security Settings in the Torbutton.
Also you should look into a Whonix+Qubes OS setup, just because there's a sandbox doesn't mean you can't get hacked.
For speed: It's not really that bad for general browsing.
I wasn’t aware of the attack surface reduction, I’ll take a look at that, thanks for the recommendation.
My ground truth for this is usually to ask full-time exploit dev friends which is a harder target, although that’s probably flawed in that if you’re targeted by someone determined it probably doesn’t matter the cost.
With Qubes you can have a Whonix-ws VM have all its traffic go through Tor, and have another VM with all its traffic through some VPN to use with streaming.
For iOS there's Onion Browser by Mike Tigas, but it's definitely NOT as privacy resistant as a Tor Browser. For Android there's Orfox and official Tor Browser builds for Android are coming this year.