social- belonging, fitting in, a sense of place, macro connection, roles, participation, contribution, big picture,
sexual- merging, wholeness, desire & desirability, operating on similar wave lengths, vibes, yearning, life/death, creation/birth/reproduction
But... Does "intimacy" always mean romantic intimacy? What about developing one-on-one relationships with non-romantic/non-family people, like a close group of friends? Is that a So domain activity, or a Sx one?
I would not say intimacy depends on who the person is, but the connection you have. I personally don't think in terms of roles and allocate intimacy based on whether it's platonic interested or not, I will say that full intensity for me is directed in the area of romantic intimacy, certain ideas, and perhaps physical activities. My desire for closeness depends on how much something vibes with me. Obviously there are restraints as to how far you can go with certain people when your connection is purely platonic, which is probably why intense intimacy is usually reserved for romantic relations.
Developing relationships can serve different purposes for different types. I often don't relate to the social firsts I come across who say they are friendly for the sake of getting something out of people (who ultimately they don't like(. I don't consider aquaintances friends, and I don't care to make connections for my own financial or social benefit. I have few friends because I only care to have relationships with people who "get me", and I them.