What is the best way to create an unattended installation file for Windows 2016 Build 1607?
Microsoft provides a tool to create these .XML files, the tool is called the Windows System Image Manager (WSIM). WSIM is part of the Windows Assessment and Deployment Kit (Windows ADK).
You can get Windows ADK via the Windows Assessment and Deployment Kit.
Here's a guide that goes through this:How to create an automated install for Windows Server 2016