CloudInit is a separate technology from PVE. A Google search for "Windows CloudInit" brings up the most widely used variant of this technology for Windows: https://cloudbase.it/cloudbase-init/
There are other variants (google: GitHub Windows CloudInit ) though most of them are unmaintained or abandoned.
This is likely because Windows has its official way of deploying things (Answer File, InTune, etc). CloudInit has always been more of a *ux thing.