I've been told by many foreigners that they consider Taiwanese men very feminine and personally I just don't see it. Possibly it's the wearing of pink by a lot of men that gives that impression, but most men and boys I met don't seem very girly to me. I would say that maybe there are different cultural ideals. I doubt that JJ Lin or Huang Yida would make it really big in America at least, because both of them do (to me) give the impression of being somewhat effeminate. But at the same time, this works out for them since both of them are quite successful here. If I was feeling in an academic mood, I might relate this back to traditional models of masculinity in traditional Chinese literature, but I won't.
At the same time, the other thing that this is sometimes used by people as a reason why Western men date Taiwanese women, (i.e. Taiwanese men are too girly and so Taiwanese women don't want to date them). I think this is patently not true simply by the non-scientific evidence that every time I go to a park at night there's some Taiwanese couple making out. I think Taiwanese women like Taiwanese men fine.
I've asked some Taiwanese people about this and their response generally seems to be either that the Taiwanese girls that date Western men are ugly and Taiwanese men wouldn't want to date them anyway, or that the Taiwanese girls that date Western men are really wild and Taiwanese men wouldn't want to date them anyway.