Hi
I got my 7400 2-in-1 about a week ago, I tried using my 7400 EFI (i5 8th gen, touch screen) and couldn't get to the installer, it would always hit 'stop' sign. After much googling I eventually came across your thread! I used your EFI and it booted 1st time, I didn't have wifi because I was using intel wifi, when I tried to swap out Broadcom kext for intel wifi kext I would get stop sign all the time, then I remembered I have MacBook wifi card and adapter in my drawer that I didn't use because they didn't fit in the 7400 (or maybe the 7390, whatever I was using at the time) so got them out, cut the adapter down as you did and now fully working wifi!
I'm not sure I'll be much help with the missing pieces to the 100% perfect 7400 2-in-1 hackintosh but just want to say a massive thanks for providing your EFi, very much appreciated!