https://forum.proxmox.com/threads/another-solution-for-passthrough-intel-igpu.176959/
check this, and when you passthrough igpu, make sure your VM display set to none or it will hang.
ok, but for backing up VM or LXC, why dont you use PBS?
https://www.proxmox.com/en/products/proxmox-backup-server/overview
you can install PBS inside another windows machine running Hyper-V, or unofficially you can install inside a raspberry...
just curious, why you need to back up those setting periodically?
normally those are just default, or even a onetime setting and forgot it thing right? isn't one time backup after modification should be more than good enough?