For me, it varies from rabbit to rabbit.
Korr, Amelia, Gizmo and Nala each get 1/4 cup per day of pellets. They are all spayed/neutered. They also all get Oxbow BB/T.
Tesla gets about 1/2 a cup of Masterfeeds and 1/8 of a cup of Oxbow. He is an intact buck and very active, so he needs more to keep weight on. He doesn't usually eat all if it, but will eat most of it.
Kraken gets 1/4 cup of Oxbow and a bit of Masterfeeds. He is also an intact buck, but not as active as Tesla. He was on just Masterfeeds a while ago, but his poops are better on Oxbow.
Lillian gets a bit less than 1/2 a cup of Masterfeeds. While she is neutered, she is also an angora so needs some more protein for her wool. She is a tad chunky, so is on a bit of a diet.
They all get unlimited timothy hay and some Orchard grass or other hay as a treat.
I don't really measure veggies, I usually take a couple bunches of parsley and cilantro and some romaine leaves and divide that up.
How much to feed does depend on the rabbit. Some need more than others based on size, energy level and just the individual rabbit. If your rabbit is not too fat or thin and is doing well on what you give, then that should be fine. If they are gaining or losing weight (and you don't want them too), then you need to adjust the amount of food.