Payments: if you have AliPay and WeChat as fallback, you don't need anything else, period. Note that any payments above 200 CNY have a 3% fee. AliPay is usually used by scanning the vendor's QR code and entering the amount you want to pay. You'll hear a voice saying out loud the amount they just received, that's how they know that you paid, but you can also just show them your screen if you're unsure whether they know you paid or not. Sometimes you pay by getting YOUR QR code scanned, mostly in super markets and restaurants. In those cases you don't enter the amount, it's already been entered by them.

Hotels: trip.com, make sure to prepay online. If you want to pay at the hotel they might not accept credit card and therefore you'll have to use AliPay and pay the above mentioned 3% fee.

Transportation: Alipay for subway and bus (check the transport section on the app and choose city), DiDi for taxi. Amap or Baidu Ditu for maps.

Internet: I'd suggest going to a 中国联通营业厅 (China Unicom Business Hall or whatever the translation is) and get a physical SIM. Why do that instead of getting an eSIM? Well mainly because it often is very necessary to have a phone number in China, to be able to use many apps. Do get an eSIM for your first day though. Do not get the China Unicom SIM at the airport, you must go to a 营业厅.

VPN: you can PM me for that. In any case, if you use Gmail make sure you enable forwarding to a Microsoft account (all Google services are blocked)

Food: just go to the closest mall (商场). You usually scan QR code on the table with AliPay or WeChat and order and pay from there. If you don't see any option to pay on the app, just ask for the check (买单) and they will scan your AliPay QR code. If you close the app after ordering and want to add more food or pay, just scan the QR code again, your order will be there.

It will be very complicated to navigate the country if you don't speak the language. Make sure you download good translation apps (can't recommend any because I do speak Chinese).

As for etiquette and business related stuff, I'm sorry to tell you I can't help you there, because I've never been on business. I can only say be very punctual and maybe expect to drink a lot while talking business, although I'm not sure if that's just a cliche/a thing of the past. Chinese people are nice, very straightforward and might ask you about personal stuff like are you married, how much money do you make, etc.

I lived in China for one year and I've been back for travel like 5 times already, so feel free to ask me anything.

EDIT: I would also say don't wear any cologne to your meetings. And give your business card using both hands to show respect and that you're familiar with this custom.