DLSS doesn’t have any performance uplift for my 3090, but it was to be expected. The 3090 and 3080 has no problem rendering a native 4K resolution, so no change in performance. I’m not sure if VRAM usage is affected by DLSS, but VRAM usage generally increases on DX12.
I made a thread about the difference in DX11 and DX12 in a 3090 for SU10 beta if you’re interested:
https://forums.flightsimulator.com/t/su10-1-27-13-0-dx11-vs-dx12-comparison-on-3090/534602