Buying online in Hong Kong (or any other foreign) Apple Store website with a U.S. credit card

I will be in Hong Kong for a few weeks and wanted to purchase a new MacBook and iPhone 8 Plus or X online from their Apple Store.

I have heard that I would be able to use my U.S. AmEx or Visa (the Apple Rewards BarclayCard) to make purchases from the HK Apple Store online, but I notice that I have to input a local Hong Kong billing address for my card. Would it be an issue if I used a local Hong Kong billing address (the home where I will be staying and using as the shipping address) instead of my credit card's actual billing address (back in the States)?

Also, is it possible to simply use Apple Pay (which has both credit cards pre-configured) from the Hong Kong Apple Store website, or via the Apple Store App (I have already changed the region settings from the U.S. to Hong Kong).

I am sorry for the lengthy post; I just want to be certain before I use my credit card to purchase anything. Thanks in advance for any and all help; I truly appreciate it!