Is trial and error the only option?

I've started developing for Google Cardboard within the last month and am having some difficulty figuring out the limitations of Cardboard on Android and even just finding adequate documentation on various topics.

For example, using certain image effects prevent anything from rendering in VR, placing UI elements too close to the camera forces you to look at them 'cross-eyed', rendering with multiple cameras doesn't seem to work (using one camera to render models, and another for UI for example)--all things I just discovered through trial and error.

VR is not an new technology, and I feel like I shouldn't be discovering all of these things for the first time by myself. It seems to me that people probably already know this stuff.

I've looked at the documentation at the following locations, but find it mostly inadequate (really, it all seems little better than quick-start guides):

• https://developers.google.com/vr/develop/
• https://unity3d.com/learn/
  
• https://docs.unity3d.com/Manual/XR.html

What is the goto reference for those of us developing for VR in Unity? In particular, for my current purposes, Google Cardboard.

I should mention that I'm also developing for mobile for the first time alongside my foray into VR, so I don't know how much of the limitations I'm seeing are mobile limitations vs cardboard limitations.