Congrats on the OW!!!!
There is no problem switching. Only difference is that NAUI requires a rescue dive with every diver certification. I've got NAUI OW/AOW/Rescue from ST. NAUI mandatory AOW dives: Night, Deep, Nav. Plus 3 more elective dives plus the Snorkel Rescue dive. My three electives were: scooter, search & recovery w/liftbag, wreck survey (non-penetration)
Now, go buy gear....