@Greg-Plamondon another suggestion. We had enough issues with pxe boot compatibility acorss different devices that we embed a custom bootloader that has an option for booting directly to a local copy of the ipxe.efi file. We use grub2win and just have its installation as part of our provisioning scripts that are started by sysprep firstlogon. Found this to work better than trying to get custom nvram type settings, this way you get it individuallized per hardware but also using a universal config file.