you failed to mention which version of anope you are looking at so I will assume 1.8...
NS_IDENTIFIED is a bit status flag of the NickAlias (na->status).. though for checking whether a user is identified there are far easier and better ways: simply use anopes API rather then reinventing the wheel. There is this nice little function "nick_identified(User*)" which simply returns true or false.
As for the CA_* constants, they nicely map to the levels as also listed in "/cs help levels desc".. VOICE lets you use /cs VOICE, VOICEME just allows you to use it on yourself and AUTOVOICE means you get it on join, but can't actually use the command.. it s similar for OP/etc..
As for checking whether a user has a level with the anope API, simply call the function check_access() which returns true or false.
Eg: check_access(User*, ChannelInfo*, CA_AUTOVOICE);