When editing the config file, changing world generation rates (I have the number set to 100000000), nothing happens. Crops (and trees) still spawn everywhere unless I turn them off completely.

(Using 1.15.2)

are you editing the file in the saves (or world) config folder? the configs folder in the .minecraft folder is incorrect.
It checks if a random number is generated is 1/chance
larger should lower generation rate unless something else is interfering with it. Are you testing with only this mod or did you add any other mods?