When launching GP Bikes in VR mode you basically have to keep the headset on at all times, which is a bit annoying. If the headset goes inactive, the screen goes black. Additionally, your monitor will always mirror 1:1 what you are seeing in VR, meaning if the headset is not facing the right direction (at the virtual monitor) you may not be able to see the UI/menu on your monitor at all.
So if you want to tweak some settings or just watch the replay of your last laps, you have to watch it through the VR headset or at least activate and point it in the right direction so that the UI becomes visible on your monitor.
My suggestion is to always show the menu/UI in regular 2D mode on your monitor, no matter where you look in VR and also displaying it even when the VR headset is inactive.
Being able to switch from VR to 2D without restarting would be great as well but I'm not sure that is possible.
BUMP
The steam version allows this with my HTV Vive Pro, I can load GPB up in VR mode and use my monitor until I get to the track, and even in session I can take my HMD off and everything is on the monitor as though I'm playing in pancake mode.
I get the same as below, always have in Steam VR. What VR are you using Vini?
Oculus.
I tried SteamVR but Oculus' native ASW is so much better than the framedrop compensation algorithm of SteamVR that I uninstalled it again.