"trap" is a term only used by people who think they're being misled by appearances. Some people get the gears in their brain stripped when they discover they were aroused
A guy who dresses quite well as a girl (or character) could be anything from a transgender candidate (Seiko in Lov*Com) to a transvestite (someone who routinely dresses in cross-gender clothing) to simply someone who likes to cosplay and Does It Very Well. It doesn't convey any information about sexual preferences by itself.
The linked website has some pretty amazing cosplay (though it all appears to be "not at a convention") ... this person should hit the cosplay circuit