Um um. dwarf--semi dwarf root stocks. The smallest tend to make changes to the crown of trees (oh, things like brittle wood etc), as well as a shorter life span.
IMO of more import to you is are you making a plantation of a few or a few acres? For just plain fewer trees, I'd select semi-dwarf root stocks IMO the resulting tree bears loads of fruit better and its up to you, as to how small you prune it. Very dwarf cultivars makes more trees per acre and may nominally increase per acre yields.
Multi-grafting: Top woods are not all created equal, The more varieties you graft onto a tree the greater the chances are for one or more of that top wood to hog out the rest. If you can't prune them into balance, go with a solitary graft, and keep the battle down to root-stock and scion-wood.
Time between plantation and harvest: well, if you're really into arbor culture, then at some time you going to do some of you own grafting. So that never again are you all out of trees. This is how you keep your plantation available to you. Peaches are going to be prone to pests that even if you spray, will kill trees. Grafting your own is the entry price to a steady harvest.
Of even more import than spraying or grafting, you need to find-read and understand chilling hours and how many your site gets. (and how many your tree needs) The fewer chilling hours your trees need could indicate too early bloom. or if your tree need too many compared to what the site gives, inconsistant bloom.
Trees with declaired resistance to fire blight or other pest resistance, are not low maintenence trees. They need appropriate care. if you don't mess with the breeding cycle of pest bugs or disease, they are gonna eat your crop, and not you.
