PBR Snow and Ice on Terrain

How do I get PBR snow and ice on a terrain?

I'm trying to make a game that has snow and an ice lake, and a few trees, and I am new to terrain textures and PBR shaders. I've download some terrains that have a snow shader, and a bunch of PBR snow shaders. Here's what's gone wrong so far:

The adjustable snow shaders that come with the terrains tend to white-out -- they don't look good up close.

The snow materials I've purchased are PBR shaders which look very good. These are not useable on the terrain as far as I can tell, because if I try to use them as the main terrain material, it says underneath the material,

"can't use shaders with tangent geometry use shaders in Nature/Terrain"

In nature/terrain the shaders do not have the same fields as the PBR snow shaders so I see no way to combine them.

I purchased a mountain lake which has a custom terrain shader but there seems to be no way to change the snow to have all the qualities of the pbr snow.

Should I convert the terrain to a mesh so I can use the PBR textures?
Would a tool like RTP help?