I think reference to the below thread is a good first step regarding DX12 related performance issues, though separating VRAM related issues though from general performance differences between Linux and Windows:
Speaking from my experience, playing Cyberpunk I see the described behaviour probably related to VRAM on a 3080 10GB. When the VRAM hits and stays at 10GB use I get alot of stuttering and frame pacing issues in open areas. It doesn’t seem to happen on every playthrough, but it is pretty regular and goes from totally smooth gameplay.
Similar issues observed in Alan Wake 2. Though in that game stuttering seems more general, it is especially prevalent when use reports as full 10GB.
In both those case something seems to occur to make it go from use going up and down to at some point being at full use and being stuck there.