I'm not sure where you mean,the device manager or the display properties, or is it somewhere else ?
If I can find it. I will test and report back.
Not sure if it makes a difference I have AMD card.
Games definitely run in higher resolution on the monitor but not sure if they are outputed to the pimax display at 1080 and then up to 4k on display.
I have tested with virtual desktop on 2k in extended mode and it looks crisper but if can fins where the resolution is listed. Will confirm. Is it in steamvr ?