Interested in the same thing!
Fighting with poor performance on a brand new HP Z machine with a AMD Radeon Pro WX 9100 .
Specs wise that card should fly and be a breeze, but it's been slowing down to below 60 fps (often 20-30 fps) without much of anything applied.
We're outputting 2 UHD screens on the card, and 1 1080p monitor for GUI. So, originally the comp was 8K (composed of those 2 UHD outputs) but we reduced to 4K comp just to speed things up (it's still not great).
GPU is often 90%+ use. 2-3 layers at a time of mixed DVX and/or ProRes material. CPU never is maxed, tons of RAM and GPU RAM available at all times. Everything is running off an insanely fast internal M.2 SSD Raid.
Any tips, anyone experience with this kind of thing? We're used to using a similar system that's almost 7-8 years old and has an old mid-range Quadro in it running a 3.2K or so output, and the performance on that is strikingly better.