My aim is the usual for an open world RPG. Closer tiles should have more polys and higher quality material, farther away tiles should have less polys and worse material (or not be drawed at all).
Also, my terrain has a natural slope. So if I set that for example from 0 to 50 it should be grass, it will not fit my map well. Also for the rivers, I have rivers that start from a high altitude and decrease. How am I supposed to work with that if I want to add water to the rivers? Some parts of the rivers will be above sea level, others below.