With both the situations you described, I presume you pay the agent on the day (certainly opening a bank account), so asking online for recommendations seems the obvious method as there's little risk. I did it on my own, but that's what I would do now. If they asked for money in advance I would walk away.
i think that is a good method, I do something similar with a Starling bank card and use it to pay for things anywhere that will accept a card. I am retired here, so I need a Thai bank account to deposit money (for the visa) and use that for cash.
you were told incorrectly. There's a lot of wrong information given by people. I used Wise for my bank transfers to Bkk bank and my non o retirement visa and subsequent yearly extensions were approved with no problems.
If you use Wise don't forget to use the correct reason, which is something like "long term stay in Thailand" (someone will correct me with the correct wording), it was the last one on the list when I used it a while ago.