The /aop command does not only affect registered nicknames, it is an internal mIRC command.
Some networks do have channel service bots, such as ChanServ, X, Q or L (The latter 3 being channel service "bots" rather than often omnipresent ChanServ being an actual "service" in itself). To use these services, you will need to register a nickname.
Channel and nickname services have nothing to do with mIRC the IRC client, they are unique to the networks they exist on and do not come with mIRC as some sort of package, they often don't even run on mIRC. You will need to contact the network's #Help channel or search their website for help with the individual network commands. Some networks don't have services at all.
Best of luck.
Regards,
