Hello,
I've a pre-version of the new Stripe Connect plugins ;which are using "account" API instead of OAuth.
In the same time, I'm performing tests for the new (new new new) recommended API for payments. It's still based on "payment intent" but can now support directly third party methods such as Google Pay, etc.
Since they remove the need of "payment method types" (with they "dynamic oayment methods" feature), it starts to be an API that we can use.... But, their future new API for the Confirmation Token is clearly a regression and does not allow the payment capture during the checkout (so just at the end page).
It's still complicated to navigate in the Stripe documentation, which contains a lot of "deprecated" API and not a clear vision on the "current recommended" one ; various pages are clearly in contradiction.
Nevertheless, if someone is interesting to test the Stripe Connect without OAuth for vendors ; you can use the "contact us" form in order to get more details.
Regards,