So, I can't speak for anyone who got a "Digital" copy of the game. I pre-ordered three (3) physical copies of the game. Here is what I know.
I got codes from both, SE and Amazon that are the same.
I got two copies from SE, the limit, to support the cause directly. So, there is a button for a Download. That DL is a PDF containing this:
Visit http://preorder.na.finalfantasyxiv.com and register. You will be notified via email prior to the launch of the game on when you can return and redeem your preorder code to unlock Early Access to the game along with instructions on how to receive your Cait Sith Doll minion and Moogle Cap digital content. You will need an active Square Enix account to complete this process so, if you want to set one up in advance, please go here: http://na.square-enix.com/members.
That is a "link" where you can enter your email, to "sign up" to be notified when you can enter your codes to be a part of early access. See this quote:
nter your email address below and we'll notify you when you can return to the site to redeem your code and download the game to get ready for the start of Early Access and play with your in-game items.
On amazon, when you get your order comfirmation they send to your email you get the direct link: http://preorder.na.finalfantasyxiv.com This is what they say:
Visit http://preorder.na.finalfantasyxiv.com and register. You will be notified via email prior to the launch of the game on when you can return and redeem your preorder code (code listed above) to unlock Early Access to the game along with instructions on how to receive your Cait Sith Doll minion and Moogle Cap digital content.
As for the codes. I ordered two copies from SE and one from amazon. The "Product Registration" of the physical copies will be in the game itself. If you got a digital copy, I don't know how that will work. however, the codes from the pre-order bonus and DL might look the same. So, for me, SE gave me two codes that follow the same format as Amazon does..
SE Codes: XXXXXX-###-XXXXXX-###
Amazon Code: XXXXXX-###-XXXXXX-###
So, I can assume that those are the preorder codes that I enter when SE contacts me, via email, from the link I signed up to be notified by email from, see above.
Does that help anyone or did I ramble on about nothing? I'm different because I ordered from two different places who gave me similar results. I can assume that what I wrote above it how it works and the process going forward. I have not reason to believe otherwise. The biggest takeaway for the bonus stuff is that you will be told when to enter your codes. Also that you can pre-order from amazon.com, get the code, and cancel your order... lol How will they stop you from doing that just to get the code?