HKG is quite relaxed as it is one of Asia'a main travel hub. If you are holding US passport, there shouldn't be a concern. If you hold a India, Vietnam or Philippines passport (or if you look like one) they may give you a bit of an issue. My dark skin friend had to sit in the immigration for a few hours even though he does not hold passport from there. Yeah they are a bit racist.

I don't think NRT check as I have been there many times and they never asked for anything.

I live in HKG so if you need to pick my brain, feel free