Cons in Korea are way different than US cons. The Comic World here in Seoul is 4,000 Won admission. They are a lot more relaxed on props. You can have pretty much whatever. BUT! You have to change at the con when you arrive, and you have to change before you leave. You CANNOT wear cosplay in public outside the con area. There are a lot of people, but I'm not sure how that really compares because IDK which cons you've been to. There aren't panels here, or any really big events at the con. It's mostly walking around, taking pics, buying fan art from the vendors, etc.
Mmmm There are quite a few boys who cosplay as girls here, specifically touhou, but they usually carry guns or are doing something crazy. LOL I don't think anyone would mind though. ^^ I've seen a few boy Miku's as well. ^ ^