> UI is sluggish

You absolutely need to pass through a GPU so that DWM.exe is properly accelerated; otherwise, it falls back to the software-accelerated WARP and the performance tanks to ~15 FPS.

It doesn't need to be anything powerful; if you have an idle integrated card that you aren't using on the Linux host because you only interact with it through a Web server or SSH (for instance, Proxmox), then pass that through. It's what I do on my home lab which runs a 9950X.

Before people raise pitchforks against Linux, this applies there, too, for the record: at work I have a Linux instance just to myself that by any other metric is ridiculously powerful: 64-core Epyc, 96 GB memory, but no iGPU, so remote desktop works very poorly.