Modify Terrain Generation

Hey guys, hope I caught you doing well. Basically, I was wondering if it is possible to modify the terrain generation of a custom dimension. I have a end-like dimension, and I somehow got the islands to spawn frequently how I wanted, but they spawn a little TOO frequently, and I want them to be more hilly/less flat.

This is what the terrain looks like now: 

This is sort of what I'm going for: 

(The yellow dimension is called Eden from a mod called DivineRPG. It's just an example of what I;m going for.) 

Thank you all so much in advance, I really hope I can make this work :)