Best Practices for VR Development - "eye-render buffer resolution" & gearVR

Hello,

From the Best Practices for VR Development sticky the following is stated:

Optimization

* Decrease eye-render buffer resolution to save video memory and increase frame rate
* Although
dropping display resolution can seem like a good method for improving
performance, the resulting benefit comes primarily from its effect on
eye-render buffer resolution. Dropping the eye-render buffer resolution
while maintaining display resolution can improve performance with less
of an effect on visual quality than doing both.

1. How is "eye-render buffer resolution" adjusted in Unity (we are running 5.6.1) these days?

2. Working with gearVR. Do these best practices also apply to gearVR?

3. Are there any additional recommendations using gearVR/mobile?

Thanks