there are lots of things you can only do in the same province. I had to go personally to sign something to get reimbursed for fraud (that big hack that affected half of Thailand) and that needed to be done in my home branch too. Letters from the bank confirming balances or printed statements also. I know it's not impossible to use a card from a branch in another province and I know about the cardless ATM. Most of the time you don't need it but any time something like this comes up it becomes an issue and you'll wish you had a local bank.
QR is far more widely accepted, you can use it with most street vendors for a 20B purchase and there's no fees either side (which is why everyone accepts it).
not with Wise, need a local bank account for that, or a bank account from a country in the region that participates in the QR system, Malaysia, Singapore, Indonesia, Hong Kong I believe can pay with Thai PromptPay QR. I think PromptPay is also cross-compatible with UnionPay QR in China but AliPay and WeChat are more common there. KB wallet from Korea.
there are still things your bank may want you to go back to the original branch for. Like if you have to get a new card, or this new biometric thing. I do think it's better to open one where you are, if possible.
I agree with you though a foreigner on a DTV is not likely on Thai minimum wage and a few thousand shouldn't be a deal-breaker to get a bank account open if necessary. They probably can get it open for less themselves if they are willing to spend the time on it but will still probably have to pay for the residence cert. Agent could reduce the wait from several months to a few days.