>My point was that giving away username/password is a terrible idea from a privacy standpoint

I'm sure you know well the reasons for this. It is not practical to move large amounts of money via credit card due to the fees involved.

As for your point on transaction history, you could always create a separate account specifically for these type of situations where you're passing your login. Even if they get your transaction history, it would be very limited.

We're going back to square one with the 'empties my account' comment. You can mitigate that but changing your password pre/post transaction so the login you use is one-time. It is inconvenient, but worth it if you do not trust the vendor and want to avoid credit card fees. If you are concerned about them getting your past transactions, you can always create a new account, or even a new bank account just for use for these type of situations. There's still some transaction history, but not nearly as much as a day to day account. I do think there's a lot of value in Plaids services but having said that, it is all a work around due to the abysmal financial infrastructure of the USA and lack of real time payments. Plaid services and requiring bank logins to do transactions does seem a bit whack, but again US payment system is even whacker.