Long story and different for each individual and base area however:
You are paid in the currency of your base area in your account in HKG. i.e. USD if you are USAB (based in the US) NOT in HKD's.
For the US there is a tax agreement with HKG therefore you pay US taxes only so you wont pay more tax. That's my understanding (I am not USAB) from chatting to the US based guys but tax is usually an individual matter.
Good luck!