Yes, I'll be feeding other things as well. I'm striving for a large variety of food items that can be harvested right from my yard. Along with my mulberry seedlings, I have several varieties of dogwoods, mimosas, and lilac tree seedlings. I'm planning to add more and more roses...I've also planted blackberry bushes, raspberry bushes, Hansen cherry bushes, blueberries, elderberries, figs, muscadines, sunchokes, loquat, and pomegranates. As much as possible, each plant is selected for both human and animal consumption. For example, the roses are mostly varieties that produce rosehips (rosehip tea and jelly for the humans, rosehips, flowers, leaves, and branches for the rabbits). Unfortunately, these plants will be several years before they can be pruned for rabbit forage.
As for how much -- my experience (for what it is) so far is that rabbits eat a LOT of fresh foods in comparison to the concentrated feeds in pellets. Probably some of that has to do with the quantity of water in fresh foods. The question of quantities and proportions (so they get the right amount of protein and other nutrients) is something I'm still working out (which is why I've not completely phased out pellets).