I would like to plant several crape myrtles from 10-15 gal pots and have them grow tall with huge canopies many many years from now.

Is there a difference in those that grow tall like trees and those that stay short and fat like bushes? If there is not difference what would be a good plan of attack for growing tall canopied crape myrtles?

Also, are there any special needs for the installation of the trees?

You've got three basic size classes:

Miniature: (or Miniature Dwarf) no taller than 24-36 inches, spread about 48 inches

Dwarf: 3-5 feet tall, maybe 3-4 feet wide.

Full: Smallish tree sized.

For a tall canopied effect, get the full-growing size, and as they get large enough, clear out some of the lower branches to encourage upper growth. Don't overdo it. Remember, pruning is largely done for the eye of the beholder, not the tree.