Planet questions

I feel like I’m asking too many questions. Anyway hi. I’ve been working on making planets for a little bit now, but there are 2 things that I have no clue on how to do in blueprints.
Questions 1(not as important, but would appreciated): how can I subdivide a section of a mesh as the camera gets closer? I think it was called quadtree or something.

Question 2(important): I know how to make simple hills and mountains using inverted sine waves, but I have been trying to figure out how to make detailed and realistic mountains. I cant use heightmaps in blueprints. There is something called the diamond square algorithm, which I dont know how to use. There were a few pictures of what I want to make here: https://www.google.com/url?sa=t&source=web&rct=j&url=https://forums.unrealengine.com/development-discussion/content-creation/89568-creating-planets-where-to-start&ved=2ahUKEwiNj9Hk0avlAhUtJjQIHUlLDzkQFjAAegQIBRAB&usg=AOvVaw38MA_Mfs3oyn8nzI58Vf7m
, just scroll down and you will find them. Anyway before I end the question, I do not need help with textures right now I’m using simple colors. I do not need help on the atmosphere either. I already have it figured out. Question 2 is more important. I will not use any written code or plugins. I dont need help with gravity yet. These planets are meant to be landed on. Not seen from afar.