Hello.
Indeed all ISO images contain VMware vSphere (ESXi host) and when installed automatically activates a demo license for 60 days, with all its active features.
Custom ISO images from hardware manufacturers include additional drivers for their own devices to the standard VMware image.
The difference is in the features that are activated according to the license that is entered, Standard, Enterprise, Essentials Kit, Essentials Plus Kit and more.
The license entry or change of licenses is online.
If you have version 6 licenses and have a current SnS contract, you can obtain the new version 7 licenses from the VMware website where you registered your VMware products.
If your SnS contract is not current, you may need to purchase new version 7 licenses.