there should be plenty of room for them to generate then.

that command is optterrain. range on it is said to be 150 meters. it is only useful where terrain was changed a lot, like in fancy bases that lagged, done in older versions than v0.150.3. as a precaution it is sensible to make a backup first, it is reported in some rare cases it can go bananas.

also fwiw, mods do not change vanilla game files. it's magic done at runtime.