Would it be possible to have the oregen spawn in a specific dimension set by the config? Reason being, I want to be able to set magic mod items into their own dimension and not in the overworld.

I see you have the trees set to specific biomes. If possible can that be configurable also?

Dimension config options for world gen have been added now in version 16.2.0.

Would it be possible to at least be able to disable default ore generation?

You can already disable the generation of ores in the config