x64boot.wim will be used by UEFI Devices with non-legacy PXE-boot.
The most tablet computer have UEFI and are not able to boot into PXE by pressing the F8 key.
The best way is to create the tablet as baremetal with valid MAC and create an OSD-task.
Some Vendors (DELL) provides legacy boot in their UEFI-BIOS settings.
Another way is to rename the files so the device boots a 32bit wim file named as 64bit.
Thanks for your answer. You won't happen to know if this is documented somewhere? I tried searching the online user guide and community to no avail.
Also, the vBoot process seems a bit obscured and not rely on downloading the boot image from PXE rep.