Oh it happens on Windows too, but wine adds some overhead, so you have less headroom on Linux. Same goes for DXVK / VKD3D - they add some CPU overhead.

Where are you getting these numbers? I have a 3080, used a 1080Ti before, and though my last direct comparison was a while (like a few years) ago, I had more like 3-5% difference in FPS in the games I tested, at most 10% in RS2 Vietnam, but this ultimately turned out to be a CPU bottleneck. I would assume (and, reading reviews on reddit, this seems confirmed) that the drivers have mostly gotten better since then.

When was the last time you used an Nvidia card under Linux? There are no performance issues compared to windows, haven’t been any in YEARS.