Welcome!
I cannot answer all your questions, however, concerning the desktop, IIRC, there is a website which has what specs you need for the desktop. Of course, that depends on what version you go with. There is SO much debate over which is best etc., I won't go into that, lol. Just something to keep in mind, 2020 has been out for 3+ years and has gotten better over time. With that being said, Microsoft is releasing MSFS 2024 sometime in 2024.
One recommendation I will make is, get a system with at least 16 gigs, preferably 32 of RAM.
As for using a joystick, I use the Logitech Extreme 3d PRO and love it!!!!