1- RT is not really there yet for VR4SU. I think maybe in future releases you would be able to use RT in production rendering but for now I think most folks use it for testing and low res draft setup of scenes.
2 - Learn to create your own materials. Loading vismats, you will not learn how to control materials or how they work. This material uses displacement, which I would use sparingly. Displacement needs to applied to geometry that sits in its own group, with no other geometry.
For a beginner, I would recommend starting on YouTube at the Chaos page and watch all the videos related to V-Ray for SketchUp. Once you learn these core principals, then look into the video series from Evermotion, which has a lot of great info for the intermediate learner.