Scaffolding is simply branching and sub-branching. Attempt to prune to the funnel configuration on the tree, favoring outward growing wood to inward on a young tree, and upward growth rather than outward growth on a mature tree. Fruiting occurs on one year old wood- the twigs and stems that grew last summer. On a one year old twig will be several buds, but only the buds that are in the middle one third of the twig are the best ones to produce fruit, although it will flower all along the twig length, cut back one year old stems by one third. This will give you a larger yield and a bigger fruit.
Peaches have a tendency to grow fruiting wood upward and outward from the main trunk.
Prune to counteract this growth pattern, to give an even branch distribution throughout the entire tree. Heavy pruning of peach and nectarine trees will keep fruit production on heavier wood, which is more capable of carrying the weight of a full crop. A good balance of growth and fruiting should be striven for. A summer pruning technique on a fruiting peach tree is to head back upper, outer shoots in late summer to allow sunlight to the lower branches and prevent dieback due to shading. The peach tree will set more fruit than it normally can carry and will drop a large number of immature fruits early on.