I believe that the ability to alter the block type they can generate on (such as changing it from vanilla grass to a mod added grass block), the density of the generation per chunk allowed, what biomes they can be generated in, and the maximum to minimum y height for generation (perhaps something like "oceanLevel = 64" which could be configured), should suffice. This could be done in one, single configure json for both, or if you deem it necessary, it is very possible to do in two separate files or more, based on how many plant types you would like to make configurable.
I believe that the ability to alter the block type they can generate on (such as changing it from vanilla grass to a mod added grass block), the density of the generation per chunk allowed, what biomes they can be generated in, and the maximum to minimum y height for generation (perhaps something like "oceanLevel = 64" which could be configured), should suffice. This could be done in one, single configure json for both, or if you deem it necessary, it is very possible to do in two separate files or more, based on how many plant types you would like to make configurable.