Would like to know also. I have a vega 56 and playing Fortnite (just to test fps ) and it's getting 20-30 fps on low..
I dual boot to windows so I always go to windows to game, but just a nagging feeling that my hackintosh is not performing as it should be.
Tested LoL on my hackintosh (see stuff & version in my signature) and it run smoothly with an average of 130FPS at any time in the game.
Weirdly enough, some game like Minecraft can't go higher than 30-40 FPS.
I think the Kext that allowed that to run was RadeonBoost.kext (to be confirmed).
Update to the latest AMD kernel patches, those fix the degraded GPU performance back to where they should be.
@JaeRadeonBoost.kext does not work for Navi since the 10.15.5 patch and Apple completely locked it out with Big Sur. And it mostly improved performance for benchmarks like Geekbench, but not for actual games