Be careful if you want to take some in-depth pic..... better ask the permission from the store owner first. But pic from outside the building or surrounding street will have no problem.
You can ask for discount even if you buy one watch, you know how the usual "bargain tactic" when you buy stuff in China, do you?..
My guess is you may try to ask them to open the case back for you if you want to make sure it is Swiss.
If you have to go back to HK after your shopping trip.....try not to buy too many at one time. HK's customs can be anal about counterfeits goods sometimes. They do random check, but usually on people who carry lots of stuff.
have fun.... hope I can join you in the future