Windows Autopilot device preparation is not a set of policies, it is a whole new profile type that changes the nature of Autopilot. It is separate and distinct from the original Windows Autopilot profiles (user driven, pre-provisioning, and self-provisioning). It is not a full replacement for the original Windows Autopilot profiles (today at least) but can be useful for certain scenarios including GCCH/US Government and assigning Autopilot to users instead of devices without pre-registering the devices. Windows Autopilot device preparation is a work in progress though and we plan on adding a lot of new capabilities to it in the near future. Check out Skilling snack: Windows Autopilot device preparation | Windows IT Pro Blog for a lot more info.

Note that today, you cannot use a custom name for devices with Windows Autopilot device preparation but this is something we've investigated adding.