eGPU Performance issue with specific game
I've been running an eGPU setup with my 2016 MacBook Pro 15" and a ASRock Phantom Gaming X Vega 56 in a Razer Core X for a few months now. So far it ran everything I threw at it including COD Modern Warfare, Red Dead Redemption 2. However, it appears that I found it's nemesis now. Wreckfest is, no matter at what GPU Settings, apparently maxing out the GPU to 100% and doesn't get more than 20-30FPS with drops as low as 8 FPS.
However, throwing the GPU in an old now-office PC (i5 760, 16GB RAM, PCIe 2.0 x16) the game runs on Ultra Settings 60FPS. I fully understand that with the eGPU setup I'm supposed to expect a Performance impact, and judging by 3DMark scores I'm looking at 30% here (20000 vs 15000 Graphics Score in Firestrike). That doesn't seem warrant 60 vs 5-8 FPS (on Ultra Settings) to me to.
I followed the guide from @itsage here but I've since completely reinstalled Windows 1909 following this with the addition of replacing the pci.sys from 1903 to gain access to my internal RP460. That lead me to the discovery that the dGPU is running at 40-50FPS on the same settings the eGPU struggles at 15-25FPS. I tried reading up on Wreckfest specific issues as well as checking common issues in this forum, unfortunately with no result. I've also seen the video from @GamesOnMacBookPro in the Megathread which seems to confirm my issues.
As of right now I'm really out of ideas as I'm failing to see why only this one game is having such severe issues so I'm hoping for some input