Iunno. 

None of those terms actually mean much of anything beyond what you want them to mean. In the end you're what you consider yourself to be. I mainly hang out in the Casual section because it's the one-stop-shop for every different kind of RP and nothing generally passes by in Advanced or Free that catches my interest.

You shouldn't really constrict yourself to a label and instead just dick around, being what you are. I've seen a guy posting in Advanced with posts that I'd barely define as being worthy of casual, but I've also seen casuals go way above and beyond with their posts (hell I know of a casual RP that casually drops like 12+ paragraphs per post, per player).

The three sections on this site are more communities of people that RP different stuff more than anything. I'm amazed this level of separation has even persisted throughout the years, as other RPing sites I've seen just lump everything together under one umbrella (for the worse imo; stuff is consistently lower quality)

You're mostly a 1x1 RPer, though, so this stuff matters even less to you than it does to most of the site.