Adjusting Display resolution Windows 11 VM (Fangtooth Nightly)

I have setup a Windows 11 VM and I can access it via VNC; everything is great except…

The display resolution on the Windows machine is stuck at 1200x800 (greyed out, unable to change anything).

How can I change this to a higher resolution?

I would use VNC just for initial setup and then switch to Windows Remote Desktop (RDP).