Cliff displacement for terrains

Hello blenders!
I’m a digital terrain artist and I’m currently starting to get into blender, I’ve been looking for a specific method of achieving a very specific result.

Basically I want to displace the cliff areas of my terrain (so the areas above a certain slope, lets say 45°) with a tileable cliff texture (or eventually even a procedural cliff texture).
Here is an example made by Olivier Vernay-Kim in 3DS Max https://www.artstation.com/artwork/Pm4Jr1


I also found this topic in the forums Procedural Terrain Displacement Cycles but I don’t know how he achieved these results and idk if they are exactly what I’m looking for.

My current method for importing terrains into blender is using the displacement modifier and I guess I’d have to use the same modifier to get the cliff displacement, but I don’t know how to apply that modifier only to those areas above a certain slope.
Another big problem is that the polygons in those steep areas are very stretched out
How do I remesh my mesh in a way to get a high density of polygons in those steep areas and a low density in the flat areas?

I was thinking of something like this for the slope based polygon density
But I have no idea how to implement this
(this is from Witcher 3)