Hey András, I like your setup and bought the game, virtual desktop and Vorpx to enjoy the same experience. However can only use the quest controllers as lightguns in virtual desktop without the vorpx enabled. When using vorpx, then I need to use the mouse as a controller. Did you set anything specific in vorpx for your controller?
In VorpX in the device selection set "Generic 3D Display" to get a half side by side image on your TV/monitor. Then in Virtual Desktop click under the screen and click on the "Half SBS" icon.