While you can find pre-made images on community hubs, these are the most reputable "lite" configurations often used to create QCOW2 images:
After installation, use Windows’ built-in tools to remove optional features (Turn Windows features on/off) and uninstall unused drivers/apps.
Finding a reliable, pre-made QCOW2 can be tricky, but several community-vetted "lite" ISOs can easily be converted into high-performance QCOW2 images. 1. Windows 7 Super-Nano Lite (blzos)