I lived in Sai Kung for a number of years, and would say it doesn't get much more expat centric than that.
When you are sitting in Steamers next, or Jaspa's, or Anthony's catch, or Cru, Hebe 101, the Duke of York, or any of the many other expat owned Sai Kung cafe's bars and restaurants in the area Booky. Take particular notice and count how many non Chinese people you see wandering around on a week night in SK town, compared to how many locals there are.
As Carang who lives in Sai Kung states, there isn't much difference in the demographics, it's largely the same types of people, all for the same reasons, living there.. Be that DB, Shek O, Tai Po, Stanley, Gold Coast or Sai Kung.. Space and view being the main attractions.