NAA and Other both go before the diamond moderators. NAA flags are also shown to reviewersreviewers, who usually handle a large portion of them.
NAA flags are intended for answers which make no effort to answer the question - that is to say, the sorts of things that are commonly posted by folks used to other forums where threads commonly drag on for days and can contain multiple related questions, tangential commentary, "thanks" / "I have this problem too" responses, etc. If you're at all familiar with such places, NAA answers will be blindingly obvious to you - and generally to the moderators handling these flags as well.
If you're at all unsure, use a custom flag and be more specific about the problem with the answer.