Booting Windows install ISOs no longer requires an extra WinHelper USB flash drive!
If your E2B USB drive was a 'fixed disk' then previous versions of E2B required you to also connect a WinHelper USB Flash drive to the system because on all versions of Windows NT6 (Vista to Win10 1609) the \AutoUnattend.xml file had to be on a 'Removable' USB drive in order for Windows Setup to detect and use the XML file.The alternative was to convert the ISO to a .imgPTN file.
This new version of E2B uses 'wimboot' which is part of the open source iPXE project here.