Well, I have some experience with gearbest, let me share it.
You can ask after sales questions in online chat without any problems, and they will get answered, until you want to return item due to damage/etc.
As already told, "US Express" is delivered to U.S. Via Yun Express, delivered between cities by FedEx, and delivered to your door by USPS. There is absolutely no reason to use "US Express" shipping, because it is damn slow. Instead, I'm using gearbest's free shipping, even without tracking number (In this case, gearbest sends with SGLBZxxxxxxx number), and it arrives to NJ in just 8-10 days. For reference, "US Express" delivery never was faster than 15 days, and often it takes 25-30 days to deliver. For example, I've ordered a flashlight on Jun 7, and it had not been delivered yet, because I've choosen "US Express" shipping.