The open mindedness of Koreans really depends on their upbringing. I know some who are party girls and are very open. Others are very cautious. No PDA, they prefer to meet you somewhere rather than you picking them up, as they dont want you to know where they live. And forget about any one night stands.
Perhaps but even my Korean hairdressers (I've had 4-5 over the last 10 years or so) were flirty as hell and they were all fresh off the boat. And believe me, the younger ones are horny and no problems with one night stands. Japanese were the same way. But yeah, obviously there are exceptions.
Also, there's many hot Koreans where I work and many (I would say most) are in interracial relationships...