That is my context and how I am running my shop at the moment. Still on php7.x 😞
I am sorry if I made you feel puzzled but I must say that I find it myself more than puzzling how to deal with PS/TB modules. Fact is, that the Mollie is damn old but runs. I use it only for Klarna (invoice, paylater) and PayPal. Since PayPal also offers paymant via invoice,paylater I am thinking about using it exclusively. But as said I find it puzzling, too, and do not know if I would use PayPal for all, if I had to use this Express checkout from PayPal and what that will mean for my shop.
Back on point, this Mollie module and the StoreCommander module I use (very old one too, but one that was a module and no Saas) hinder me on going for php8x.