First, I can assure you its a Surface Pro 3. Unfortunately, its the only one I have at the moment so I cannot verify whether multiple SP3 share the same vendor class. (although I am guessing they may)
The other question in regards to changing to snponly.efi, it could have been I wasn’t pointing the BC_EFI entry.
pxe-service=BC_EFI, "Boot UEFI PXE-BC", ipxe7156.efi
Wrong architecture entry
pxe-service=X86-64_EFI, "Boot Surface UEFI" snponly.efi
Tom, to answer your question, yes I believe you can mark this as solved.
Thanks for all your help.