I probably emphasize diameter ratios more than anyone on this forum, although not simply in the context of the relative diameter of scaffolds.
If a scaffold is more than half the diameter of the trunk it often leads to a weak union because the trunk cannot generate enough tissue to affectively wrap around the scaffold at the union. In the worse case this causes inverted bark where branches push against each other with every year of growth, often leading to split trunks of codominant leaders. An oversized and excessively upright scaffold becomes a competitor with the assigned trunk and can lead to the overall destruction of a tree.
I didn’t address the oversized top right branch because I assume the cut to the trunk will be made below that. However, that is the cut I would make because I train even peach trees to a central leader for the first couple of years before making a cut to create an open center tree… usually. Almost all my nursery trees are trained to allow the installation of squirrel-coon baffles.
To me, understanding the significance of ratios of branch unions where there is always a dominant member of any coupling of larger wood is one of the fundamental aspects of truly grasping the mechanics of pruning. I am continuously guided by the principle of ratios when doing all the pruning I do and I’ve never met anyone who spends more of their time than I do pruning fruit trees.
Apple trees are a lot more complicated to prune than peach trees, but peach trees require a different kind of attention to assure they don’t get permanently out of shape because some mistakes cannot be corrected later on- most varieties don’t generate new vegetative growth from old wood. With an out of control apple tree you could usually make a single cut leaving a stump and the tree will generate rapid new growth that a skillful pruner could use to create a brand new tree. Such a cut would generally kill a peach tree that requires vegetative buds fully formed the previous season to generate new growth.