The NX55xx/NX75xx can adopt the AP76xx series APs. We strongly advised that the NX/AP76xx run v5.9.3.2 (just released) to avoid any known/resolved issues since the release of the AP76xx.
You will need to be a registered user and after registration, you can obtain WiNG 5 documentation, including User Guides, which has everything you need to verify adoption:
Extreme Wireless WiNG