While informative, it didn’t talk about the terrain material at all. I will however start watching the twitch streams.
This terrain is unique b/c
Ends in single M_Landscape_SandRock node?
Uses MatlayerBlend_~ instead of LandscapeLayerBlend
Uses BreakMaterialAttributes and MakeMaterialAttributes
Uses Material Functions/Expressions
All that makes for a lot of learning and understanding of advanced material editing, which I want 
Also this setup makes it fun to edit the terrain.