

Yes, the baseband is isolated on all of the officially supported devices.
And
The mobile Atheros Wi-Fi driver/firmware is primarily a SoftMAC implementation with the vast majority of the complexity in the driver rather than the firmware. The fully functional driver is massive and the firmware is quite small.



Yes, on the spot.
People will tell you they have their wife on it.
I have everyone up to my old mother on GrapheneOS and after the initial fiddling with permissions, I don’t even touch it.