Hay is number 1. Unlimited amounts of grass hay (no alfalfa/lucerne after 6months old)
Limit pellets to 1/4 cup per 5lbs of body weight.
Veggies, do what you want as long as your rabbit still eats lots of hay. You will know your rabbit best.
My pair got a 2quart dog bowl filled every morning.
Lay off the brussel sprouts though (half of one to 1 per day max). Try and stay away from veggies that could potentially cause excess gas like sprouts and cabbages. (And just use less of the high calcium high oxalate foods like kale parsley spinach, their totally safe just dont give 2cups of kale a day haha).
Herbs like cilantro, parsley, dill, basil, greens from root veggies like carrots or turnips are fantastic!
Leafy greens like red/green lettuces. (Just no iceberg) some types of lettuces can be bitter so know your bunny.
Fruit / carrots are to be a treat only. I would say no more then a tsp/tbsp per day. Honestly no fruit is needed at all. But if you learn your rabbit loves banana that might save you if you have to give meds at some point.
So no not 75% because most of their diet should be hay. But 1/2 cup every other day is just sad.
Somewhere inbetween. Make it up as you go
there is no set in stone rule you have to follow. You know what your bunny will need.