I don't know anything about orchards, i'm guessing the goal is to grow apples. Do you intentionally keep those trees small? How long before they start bearing fruit? How many pounds of fruit per tree do you get? Sorry about all the uninformed questions, i am truly curious.
I will answer a couple of your basic questions, however if you are truly interested this video which is long really explains things much better than I ever could.
The trees are planted on 12' rows with 36" between trees, height is kept to 9' max.
Feathered trees are cropped the year after planting, this is called the 2nd leaf.
Yields are projected at 1,000 bushels/acre in 5 years, 40# per bushel.
This is the future of orchards and many are converting to this tall spindle system.