You can run games at every resolution/aspect ratio you want. However, different aspect ratios make sense for different things.
If vorpX can handle that for a game, let it do its thing. It knows what aspect ratio is best under which circumstances.
If vorpX can’t handle it for a game, use the below rule of thumb:
For ‘Play Style’ set to ‘Immersive Screen’ or ‘Cinema’ widescreen resolutions (16:9/16:10) are typically what you want.
For ‘Play Style’ set to ‘Full VR’ choose 4:3 resolutions unless you have to reduce the ‘Image Zoom’ slider a lot to compensate for missing FOV. Widescreen resolution otherwise are a waste of GPU power with ‘Full VR’ since a lot would get rendered that never is visible in the headset.