I’ve only played around with this a while ago. Looks nice and interesting, but also still in a very early stage.
Now there’s some documentation available which you can check out
https://docs.mendix.com/howto/mobile/how-to-ar-simple-cube
https://docs.mendix.com/refguide/ar-widgets
I’d recommend to first start with a normal Native Mendix App. Also consider what exactly you want to achieve.
regards, Fabian