yes as in it’s just another rom flash, but your userdata very very likely will not be able to migrate. I tried in the past and solved some bugs, but overall not worth the time - make backups and restore or just start fresh
partition table will not change for the lifetime of the device. Haven’t flashed the FP3 individually for a longer time now, but usually I just resort to sideloading the one zip and be done. It will flash to the inactive slot in the A/B scheme so orient yourself within fastboot to not get confused. In doubt you can flash both slots to parity (some sideloadable scripts can do this for you too)