There are many ways to feed rabbits. Some people have success raising them on mostly hay diets, with very small amounts of pellets and some safe vegetables/leafy greens. Most rabbit breeders and showers (at least that I know of) follow almost the opposite feeding program, giving each rabbit a set amount of pellets a day and rarely offering hay, much less greens. I've always raised my rabbits the latter way, with the results being happy, healthy rabbits with good flesh condition, quality coats, fertility, and productiveness.
I don't raise Netherland Dwarfs, but I do raise Mini Rex, which are a similarly sized (though slightly larger) breed. I free feed Mini Rex kits up to about 10 weeks of age, then switch to giving each rabbit 1/2 cup of pellets each day. If a rabbit seems slightly "off" or is stressed out, I give a handful of timothy hay. Rabbits having trouble maintaining weight or nursing does with large litters get supplemented with some calf manna, sunflower seeds, or oats. Otherwise, my Mini Rex eat just pellets. The pellets I use have about 16% protein, but 17% or 18% is fine.
You could try the mostly-pellet method and feed your NDs 1/3-1/2 cup of pellets each day, or the mostly-hay method, and feed only a few tablespoons of pellets each day, but unlimited timothy hay and some vegetables (parsley, bok choy, romaine lettuce, kale, etc.). Either way would probably work; the choice is up to you.