I've recently got a Quest 2 and saw this game available via App Lab. However, If I purchase through App Lab do I get access to the PCVR version also somehow or should I buy through itch for both versions? If I buy through itch anyway though can I get a key to get the App Lab version, just because it'd be nicer to install it through there rather than going through SideQuest.

On itch you get an app lab key + a zip with a steamVR version 
If you get it on app lab you only have the app lab version