I have an XFX rx 5600 xt - the card works great. No vBIOS flashing necessary, it had the updated version and ran at 1780GHz out of the box. Release date was a long time ago so that really really ought to be the case for everyone by now; check with the seller.

Drivers wise, you need to be using relatively new Mesa packages. If you try Ubuntu 18.04 or something you're going to need to get newer Mesa versions from a PPA. 20.04 has everything you need already.

The card works well with Radeon profile for custom fan speed curves.

Random point, for $140 you could get 4 sticks of 8gb ram instead at 3600mhz clockspeed instead of 3200: https://www.amazon.com/Corsair-Vengeance-PC4-28800-Desktop-Memory/dp/B07RM39V5F/ref=mp_s_a_1_3?dchild=1&keywords=16gb+ddr4+3600&qid=1592771893&sr=8-3

Technically any RAM will be supported in your motherboard so long as its DDR4; but yes 3600mhz RAM is ideal for AM4 CPUs. Depending what games you play, or applications you use will best determine how much RAM you need, but in saying that if you wanted more there's no real harm in it.

I'd suggest starting with 16gb 3600mhz RAM, and if you feel more and can afford it, get more. I recommend these for their price https://www.amazon.com/Corsair-Vengeance-PC4-28800-Desktop-Memory/dp/B07RM39V5F

yes you would, this is a decent set of sticks for a reasonable price
https://www.amazon.com/Corsair-Vengeance-PC4-28800-Desktop-Memory/dp/B07RM39V5F/ref=sr_1_3?dchild=1&keywords=16gb+ddr4+3600mhz&qid=1597404216&sr=8-3