Someone more knowledgeable needs to chime in especially regarding your specific cards but as far as I know AMD graphics drivers come with the kernel these days, I have rx460 on f28 and I didn’t need to do anything regarding drivers.
I do know that the R9 390 was bugged for a long time, but supposedly it’s fixed, but it’s not working for me.
My resolution is stuck at 4:3 1024x768
and I run into the issue above when running ./configure for mesa