CommodoreAmiga A thing to take note is, some QR code you see on merchant (e.g. Food court, street food?) might use their own personal QR to accept payments from customers, rather than a proper business merchant QR. This is also happening in Malaysia actually.

If it's a personal QR, then it'll be considered as a peer to peer transfer (just like transfer money to your friend/family). Alipay and WeChat don't allow such transactions if it is linked through international bank cards.

The acceptance of TnG ewallet in China, also depends whether the merchant supports Alipay+ or not.
If it supports only Alipay but not Alipay+, then you'll see "invalid QR" error on your TnG ewallet app.
In China, unfortunately, you need to manage your expectation that card terminal machines are not found in every places, unlike in Malaysia here. Even if that merchant/shop in China has a card terminal machine, VISA and Mastercard may or may not be supported, and it may only accepts if it's under UnionPay (银联), so better that you ask the merchant staff whether it accepts VISA or Mastercard or not. If it doesn't, then your Wise card or whatever Malaysian bank cards also won't work.

China don't block banking apps one, so it's fine.

You said you booked a hotel via Agoda, you've paid it or you'll pay it at the hotel physically? If you'll pay there physically, assuming the hotel room fee definitely exceeds 200 CNY, or whatever stuff that you want to pay that exceeds 200 CNY, then the sequence of the preferred payment method if one fails, shall be:
Card payment (Wise Card, GX Bank, BigPay,...) > TnG ewallet > Alipay (bcuz of the 3% fee) > Cash

Alipay or WeChat Pay is accepted pretty much everywhere there, so making sure that your Alipay app is linked with bank cards (Wise) will be very helpful.

If you don't have enough cash, you can use China's ATM to withdraw cash using your Wise card.
Make sure don't exceed 2 ATM withdrawals in a calendar month, or cumulative equivalent amount to RM1000 in a calendar month. Else, there will be additional fee from Wise from 3rd withdrawals onwards or exceed RM1000.

Some merchants accept local Unionpay card only, not foreign Unionpay. Try to open a Savings account at Bank of China (Malaysia) or ICBC Bank Malaysia and ask for Unionpay debit card, it may be accepted in China.

Agoda is not a China company, you pay to Agoda Singapore in RM with Visa. However the hotel may ask you to pay deposit when you check in, then you need to pay in cash (refundable when check out) if international card is not accepted.

Starbucks and Disneyland accept Visa/Mastercard. But don't expect McD and KFC accept Visa/Mastercard.

Now Beijing's urban transit accept Visa/Mastercard, not other cities yet. Just enabled a few weeks ago.

China-issued UnionPay card would work well, provided if it is issued in China.

Even if you apply UnionPay card from Malaysia banks, it may still be treated as an international bank card in China also.

Open a China bank account and get a China-issued UnionPay card would make better sense if you intend to stay in China for long time, like for study or work. Otherwise, you can forget about the option of getting a UnionPay card.

What is this Alipay 3% charge? Every transaction i made in China with Alipay will have 3% charge? 
If you link a non-China issued bank cards (such as Wise card) and make payment of more than 200 CNY in a single transaction, Alipay/WeChat Pay themselves will charge you 3% foreign transaction fee of the entire amount.

To avoid this fee, make sure the amount doesn't exceed 200 CNY, or you split your payments, provided if the merchant is okay with that. Meaning, if the payment costs 280 CNY, so you pay 200 CNY first, and then pay 80 CNY.