So you have retail and volume licensing keys. You will get different products: These are FPP (Full Packaged Product) and Volume Licensing. This is where documents such as the Product List and Product User Rights come into play and more...
What key you use for installation doesn't matter. You can always change to a different key later with one command. So the real question is not about what key to use for installation, but what key to use in the long run. If you have a legitimate product key, then it doesn't matter what key you use for installation. After Windows is up and running, you change to your legitimate key. If you don't have a legitimate key, then what key to use in the long run depends on what sort of trick you intend to use in order to get around the need for activation, if any. Based on past experience, in the future you will probably be able to use (emulated) KMS activation, so use the GVLK. Don't use any tools for removing watermark.