I do this with QEMU/KVM with passthrough of an RTX 3090, an NVME SSD, and one of the onboard USB controllers. Works like a charm, though the VM boot time is very high if you allocate a lot of RAM to it (there's some kind of bottleneck in the linux kernel when pinning huge amounts of consecutive memory pages while using passthrough, don't fully understand it but it's a known problem).

Performance is indistinguishable from native, e.g. I can easily drive the screen at the max 144 Hz refresh rate, G-sync works, etc. I did put some effort in figuring out how to pin CPU threads to cores, optimize for the CPU core topology so Windows only gets cores on the same CCX (it's an AMD Zen 3, before that it was Zen 2), etc. But all of this is documented in many places.

Do note that depending on your motherboard not all of this is possible if the chipset & BIOS do not provide enough MMIO isolation, you might not be able to isolate a USB controller or a separate NVME drive, or you might get only half the PCIe lanes for the passthrough GPU if you need to use the other full-lane slot for something like a second GPU.