A lot of literature says to wait for a dry spell. That would be optimum, but there are few dry spells here in the spring. We don’t pay attention to precip when pruning. If pruning during the early part of the growing season, I’ve found the trees will callus without canker without too much problem.
Also for folks who have reasonably cold winters like here in the KC area, pruning trees hard before or during winter can kill a young tree. For that reason alone, we try not to prune trees just before or during winter, or if we have to, we try not to prune young trees too hard.
We don’t worry too much about that. The trees will mostly even themselves out eventually. The largest scaffold will always be the largest, but the trees fill in regardless. One issue can occur where two lower scaffolds selected at exactly the same height on the tree will starve all the nutrients from the third scaffold higher up. That scaffold can sometime lack vigor to the point it does affect it’s performance substantially. That’s why I like to keep at least a 2" vertical spacing (I prefer more) between scaffolds.
Our trees are substantially larger 18’ diameter. I’d keep a minimum of the first 2’ of scaffold clean. Then you can allow some shoots to grow. If you want to try to get a little bit of fruit earlier, you could just leave shoots the first 2’ of scaffolds, then prune them off later, as the tree gets larger. We eventually prune everything off for about the first 3 feet of the scaffold, when the trees are mature.
You might think that all the trees would have a 6’ diameter donut hole in the middle, but that’s not true. The canopy works it’s way back in to fill the middle.
One thing to watch about forks on a scaffold is that you want all the secondary branching to have good collars, so they don’t break off. In other words, try to select secondary branches with the same good crotches as the scaffolds do. Look for collars forming, if possible. Shoots which come off secondary branches really don’t matter. They generally don’t get big enough to cause a problem and break off. Even if they do, it’s not a major branch, so no big deal.
Make sure you don’t over think it. There is pretty much no such thing as a perfectly pruned peach tree. I have a guy who has worked for me for four years. He prunes as good as me. Yet he and I never prune a peach tree exactly the same way.
If you leave something, you can always prune it off later, so you can delay a decision somewhat. Just make sure you don’t leave too much. That’s one of the biggest mistakes new home growers make. They are afraid to prune their peach tree. But these young trees can be whacked mercilessly during the growing season.
You’ll want to cut the scaffolds back to where they are growing more horizontal (vs. almost straight vertical). Or cut them back to a secondary which is growing more horizontal.
Here is an old thread where I showed pruning before and after pics. The tree in the pics is a Contender which wants to grow more upright. Peach trees must be forced to grow more lateral, if you want to be able to prune, thin and pick fruit from the ground.
If you go down to the end of the thread, I have a pic I took last spring of the same tree, so you can see a sort of evolution of a 4 year old peach tree.