Hey guys. On ipad so quick reply but will reply in more detail later.
The depthfade thing that made the opaque material appear translucent was using the tempaadither node hooked up to pixel depth offset, mixed with a heightmap. This creates a more interesting intersection when jamming meshes together and most rock and tree assets in paragon are using it, with some displacement texture contribution. Then we have other materials which do PDO and bumpoffset which can look great for certain textures and is cheaper than POM.
I think for now POM is my ch faster than tessellation. The river case can be handled in a simple way if you assume the water is a flat plane. Ill post more on that later.