Which would be faster for a KVM windows VM: Virtio drivers on an nvme, vs a passthrough SSD?
It was related to an M.2 SATA SSD but I made some benchmarks some time ago, maybe this helps you: Help needed: Passthrough a M.2 SATA SSD
My Western Digital NVMe drive gets a significant performance penalty for using virtio over PCI-Express passthrough on macOS. Not sure on windows.
I played around with various storage scenarios on ssd recently and ended up picking virtio sparse raw file containers on a zfs filesystem. Passthrough device did eek out a few % in performance but the manageability benefit of container files + snapshots over raw device made it the winner. I run virt-sparsify and zfs snapshot the containers in a nightly script and it seems to be the best of all worlds: fast, efficient space use + zfs compression, easy backups. If you’re on nvme, all the better, you probably won’t complain about virtio performance.