I'm think you may be a bit confused. You can create a pre-preorder, by configuring the duo you want in advance of preorders opening up on the 16th. You cannot yet actually preorder the Duo yet. If you did the pre-preorder configuration you can remove the configured device in your Apple Store App. Or you can do nothing as your order can't go through until you actually fully confirm the order at checkout.
In other words, the pre-preorder does nothing more than permit you have the order waiting for you to complete on the 16th, when preorders officially open. It will NOT be placed unless you complete the preorder at checkout on or after the 16th.