I am trying to restrict all spawning and worldgen to one dimension (The Lost Cities) I have successfully got it to only spawn pokecube mobs in that dimension but I don't see a config to restrict worldgen to one dimension. All buildings/structures still spawn in the main world dimension. Is there a way to restrict everything to be in one specific dimension?

For worldgen, you will have to learn how to make datapacks to modify where structures spawn
https://minecraft.wiki/w/Tutorials/Custom_structures