Well, I tested it. if I inject intel in order to use quick sync, VEGA's fan will spin at high speed all the time, even opening a youtube video on Safari won't change a thing. But if I remove injectintel, and open a video of YouTube fans will spin normally! the caveat is I have to keep Safari...
We have a topic dedicated to it : https://www.tonymacx86.com/threads/post-os-x-luxmark-opencl-benchmarks.147035/
Look for it there are some Vega related benchmarks there.
I'm qouting my post from the " Post OS X Luxmark OpenCL Benchmarks" topic.
I'm getting around 15sec for BruceX. In same...
No, I'm using 17,1
and you only need to drop lilu and whatever green kexts, noting else + You are not suppose to inject ATI either.
Try to have you config.plist as clean as possible at first. step by step add necessary changes.