Landscape system, related features and issues

OK, I am new here, so forgive a grommet.

How many Levels of Detail can you have in Unreal Engine for Terrain? Is it restricted to 2, or could you conceivable go to 23 levels like in most Terrain Servers.

That leads me to the question of using a terrain server like Cesium. Has anyone interfaced that into a global Unreal Engine?

Chris