I can't answer for Fedora, but for Mobian (Mobile Debian). It works reasonably well with a USB-C dock and external keyboard/mouse/monitor.
A lot of apps works well between both of you use phosh. Purism (the software dev behind phosh) developed libraries to enable apps to switch between desktop and phone mode (it's called libhandy).
Yup, others have done the docked thing after installing gnome-shell. Haven’t tested it myself since I have an older PinePhone where this wasn’t functional.
I wouldn’t say any apps work “well” on mobile - but everything that works on mobile is usable on desktop.
A lot of apps works well between both of you use phosh. Purism (the software dev behind phosh) developed libraries to enable apps to switch between desktop and phone mode (it's called libhandy).