Usually setting the cache mode to “none” gives the best performance, assuming you’re using the virtio interface, instead of SATA/SCSI. This is a common mistake most newbies make when installing Windows, because virt-manager defaults to the latter, which gives poor perfomance. The same goes for the network btw, you’d want to use the virtio network interface instead of the emulated NIC. So before you install a Windows guest, make sure you change both those interfaces.
After changing the hardware interfaces, what you’d need to do (with Windows guests) is you’d need to supply the [virtio drivers](github.com/virtio-win/…/README.md, which you’ll need to provided to the Windows setup (via the virtio driver ISO) when prompted.
But if you’ve already installed Windows, you’ll need to install all the virtio drivers first and then update the interfaces after you’ve powered off the VM.
And in case you were wondering, this isn’t an issue with Linux guests, since virt-manager defaults to virtio hardware, and drivers aren’t an issue either.