So I recently gained the vote-to-close privilege, but I'm often not sure what the most appropriate close reason is. NARQ and Not Constructive seem very similar, and I see a lot of questions being closed as Off Topic but which I would categorise otherwise.

Off Topic implies to me that it's a valid question and would be appropriate on another SE site (which may not exist yet). Since shopping is not appropriate on any SE site whatsoever, it's not just off topic (I would probably go with Not Constructive), but I see shopping questions being closed as Off Topic. (For example, this question.) It seems to me that Off Topic is used when a question is off topic and a crap question which shouldn't be migrated, whereas I would say that Off Topic should only be used if there doesn't currently exist an appropriate SE site for the topic.

Also, what is the distinction between NARQ and Not Constructive? I would close this question as NARQ because it fits into "overly broad", and this question as Not Constructive because it "solicits opinion", but the former has two votes for Off Topic and the latter was closed as NARQ.