Amazon's overseas purchase in China is actually just a price reduction promotion strategy. The price is lower than domestic Amazon but higher than other overseas Amazon, but some goods are not sold in other domestic shopping malls but overseas.
Amazon also supports UnionPay, but I suggest you don't use UnionPay. UnionPay borrows other payment channels overseas, and it is very troublesome to refund.
Amazon's overseas purchase itself is also a special section of China Amazon, and all of them support UnionPay.
Some Amazon products in the United States support global direct mail, so they are all shipped from the United States and sent to any destination in the world. Like JD.COM, Amazon can guarantee authenticity as long as it is self-operated, but it is hard to say for third parties. But the laws in the United States are much more perfect than those in China, and there are few fakes, if any.