The answer to your question is near the bottom of the Amazon product page:
"Q: Will the amazon boxed version here, be steam, origin or no drm like the gog version? Anyone know please?"
A: It will be no DRM but will come with a GOG code for an online backup copy, the pre order copies will require the download of a small file to allow play so not quite as DRM free as previous Witcher titles.
Here is the full FAQ from the CDPR Forums : Do I need Internet access to install the retail PC version of The Witcher 3: Wild Hunt? A: The initial, pre-premiere retail PC batch of The Witcher 3: Wild Hunt needs to download a file from our servers to allow play. This file will either be downloaded automatically during installation process or you can choose to download it manually from a dedicated website.
Since we have no DRM in the game, this is a security measure we needed to incorporate so the game doesn't leak during the production process. No worries, the file will not be big. Copies of The Witcher 3: Wild Hunt produced after launch will not contain this security feature.
Q: Will there be any sort of serial number provided in the retail PC box?
A: The game does not require any serial code to install or play. However, each retail PC copy of Wild Hunt will contain an additional GOG.com game code for The Witcher 3: Wild Hunt. See below for details. Q: What is the GOG.com game code found in the box used for? The game code grants you access to a digital backup copy of The Witcher 3