Ok I tried it out again. I had to unplug the HDMI cable from my “TV as monitor” because powering it off wasn’t enough to stop it from being detected. Once I did that the virtual monitor worked perfectly.
I played Dishonored. I cycled through a few of the Vorpx resolution presets and they all worked and none said the monitor didn’t support them.
I used a Samsung Odyssey Plus WMR headset. Played with a 360 gamepad.