Both Alipay and WechatPay began to accept international cards now. But if single transaction more than 200 RMB, there is 3% fee, so be careful there

the answers to both of your questions are "Both"

Does the error message says "insufficent balance" or "QR cannot be recoganized"? I believe it is the latter. what actually happened is the the QR you are scanning is other banks' Personal QR, not merchant QR. that's why it is rejected

These unauthorzied transactions are ALL "Non OTP transaction" from online merchants. Per visa rule, Merchants are those who decide whether OTP is required, but merchants also needs to bear fraud risk. So non OTP transaction refund is almost certain, but it does take 14 to 30 days to get the money back. If you want to be safe, within TNG app visa security center, there is one option to disable "non OTP transactions". It can pretty much stop such issues, but you will have to enable it for online non OTP transactions.