If you look at Richard Rohr's book, he says that the sexual types are the gut triad, the social types are the heart triad, and the self-preservation types are the head triad. I have also read in several places that all of the gut types are power oriented. They take the feelings of aggression which power and aggression are sort of one in the same; they feel in their body and for the Eight, it is managed through overt aggression, the Nine manages through passive aggression, and the One by channeling it into socially approved ways (being next to the social/heart triad) with perfection.
Despite what I keep hearing people say on these big personality websites all over the place, I have never seen any information that caused a light bulb to go off on how any type would be sexual or social or why, and how it all pulls together. It only made sense to me when I read Rohr's book.
So to help you see where I am coming from, look at the most overt types in a triad, because they really speak for the rest of the triad. So for the gut types, the most overt gut type, the Eight, their biggest struggle or vice is lust, meaning they like connection, which is what all the sexual types stand for. But what the Nine and One feel, the Eight just lets it all hang out. Another example, since reading Rohr's book, look at this so-called Sexual Three. I have seen some who have the look of sex appeal and such, but even with that I believe they are dominantly a social fix, because regardless of how fixated they are on relationships, their need for trophies always rules. It seems we could go on and on getting into the nitty gritty on this.
This is another website that I think sort of supports my philosophy.
http://www.enneagram.net/subtypeschart.html
And according to this website, if you are a sexual type, your identity is your relationship. I could never imagine a Three think this way.
If I am wrong and somebody has some information or a way of explaining it that adds up, then I really do welcome it, because the other ways it has been explained just doesn't to me so far.