I just got a RX 580 and every other game is running fine, on csgo my var and svar are extremely high and my fps is consistently 10-20, I had a 1050ti beforehand and it was fine, I have tried disabling full screen optimizations, fiddling with wattman and trying an array of launch options. I also rolled back drivers but nothing seems to be working.
When I had trouble with this game I found this video and set it the way he says and it worked great for me.
CS:GO - AMD Profile Settings for Best Performance (FPS Boost) - YouTube
try ddu and install the current driver fresh