I just use them for rootstocks. Once I moved about a dozen seedlings in the orchard area, intending to graft them. I never did get them grafted and so they grew out. I let a few of them fruit, and although the peaches weren’t as good as cultivated varieties, they were decent, and much better than anything the stores sell.
Peach seedlings don’t come true to parent because of gene shuffling in the fertilization process. Although I’ve been told peach seedlings more closely resemble the parent than apples. I don’t know if this is true, but I’ve seen that info. often repeated.
I could see where peach seedlings would be truer because they are pretty much self pollinating, and even if a flower is cross pollinated by another tree, that tree will have to be a peach (or a nect, which is a fuzzless peach - ignoring the fact that peaches can occasionally be cross pollinated by other stone fruits because it’s rare).
On the other hand apples can be cross pollinated by ornamental crabs, and frequently are. I can’t imagine this would produce a very edible fruit.
Here is a link with some basic info about peach/nect genes.