Well Taiwan likely suffered from the same things that plagued Chinese colonization efforts in the south - malaria, hostile natives, limited farming space, and so on, so unless there was a really strong official push for colonization (which in turn, would probably have required the Chinese court to have an acute understanding that the land was not yet 'theirs'), a Three-Kingdoms-era Taiwanese colony would probably be limited to OTL small settlements and limited administration, to be abandoned as soon as greater pressures starting coming down from the North.