There is a discussion found bellow in X4 Foundation forums, where at GPU bound scenario both RDNA1 and RDNA2 GPUs do not perform properly with the Vulkan game engine.
One user has 1080Ti, 6900XT and 3080Ti and run tests at 2560x1440 and was perplexed why the 6900XT is so slow.
Another user joined in with a 6800 and myself with a 5700XT AE.
GTX1080Ti shows 60% higher fps compared to watercooled and overclocked 5700XT AE, and 10% faster than the 6800.
3080Ti is 45% faster than the 6900XT which is barely 25% faster than the 1080Ti.
All GPU scores are at 100% GPU load and max speeds.
Is there a driver issue? Is this a game engine issue?
1080ti (evga sc2) = 120 fps - 125 fps
1080Ti (strix gaming oc) = 125 fps
3080ti (gigabyte aorus master) = 232 fps - 238 fps
6900 xt (amd reference) = 160 fps
6800 = 115-135 fps
5700XT = 70-80 fps
6700XT = 80-95fps (update)
Another user tested the set settings with a Radeon VII
72-108 FPS, ~195 watts GPU usage, ~1750MHz Core, 1200MHz vRAM - Increased vRAM speed and undervolted GPU.
75-113, ~280 watts GPU usage, ~1900MHz Core, 1200MHz vRAM - Heavy overclock with +20% power limit.
68-103, ~190 watts GPU usage, ~1750MHz Core, 1000MHz vRAM - Mostly stock settings except for an undervolted GPU.
The low end of the FPS is at the same scene with all the AMD & NV cards.