To be Honest, they look rather Boring.
For the Potatoe Fields:
I wouldn´t make the whole surface covered with the same Ressource.
I would think of two different ways of Improving:
First (In my Opinion the better one):
Use "SurfaceAndGroundControl:" to create a Pattern. For Example I would maybe use it to make dirt Paths appear in the Biome, maybe with a grass border to the Fields.
Make the Potatoe Fields Ressources. That would spread them out ove the Field, and let some other Plants/trees grow there. Looks much more Natural that way.
In Both approaches you could mak a small "Bump" of Grass as Object that may spawn. If you make the Custom Object befor your Ressources there may Spawn Trees/Plants on it. I would think that could also look nice.
The Moor Biome is one I actually like. But:
First: The Colors are off, I would actually darken them a bit. (If you dont use Forge, replace to Swampland might do the Trick).
Then, I would increase the amount of Water, and add some trees, something with hanging leaves/vines. Not too much. Just a few. Or maybe an Island Biome with some more trees.
You wrote they look like Vanilla Plains but better, if you go for a Prairie I wouldn´t go for the Plains Look. While I´m no expert on landscapes, but when I think of a Prairie I dont think of green fields.
With that in mind, I feel the Colors are also off. I would go a bit in the direction of the Savanna Biome.
But thats just my Opinion.