Although all the prices are in Chinese Yuan, agents want you to pay in USD.
That means, realistically, TransferWise is used to convert from your local currency to USD.
Americans: Consequently, if you have USD, which will mostly apply to Americans, you won't save anything on the conversion. However it might be worth considering TransferWise as a payment gate in favor of DHgate and other Chinese options, for privacy and security reasons.
Non-Americans: If you are not American, you can save money on every payment, so Transferwise will definitely be worth it.
With that being said, Wise has lots of uses outside of agent shopping, and I think everyone should have an account.