The OP6 is an unofficial build and has yet to be tested. RTL8188EUS support has been reported by the developer but has not been verified.
The OP7 build is the top of the shelf NetHunter device and supports all functions. RTL8188EUS will be added as soon as it is proven to work. So far I have not been able to compile it without conflicting with RTL8812AU.

You can find a list of recommended devices here:
https://kalilinux.gitlab.io/nethunter/build-scripts/kali-nethunter-devices/nethunter-images.html

Hope that helps.