I can’t say i’m afraid, i used Stripe with Snipcart, so i don’t know what happens.
I don’t believe i have ever seen a store silently talk to paypal in the background.
i have been using stripe, paypal and mollie before, the later 2 both with leaving the site and returning after completion, even though the return does not matter since the api calls the server at some point anyways…
seems paypal also has some rather new alternatives, gotta investigate some more on that…
When I did a small shop with kirby I used Paypal with its cart and checkout. That worked out extremely well, especially as my client wanted the simplest possible solution covering a plentitude of payment options and needed different languages supported but had only little money. Securitywise one can also setup verified products in Paypal so in the end it resulted in the ideal solution. Always worth a try to me and should not be too hard to implement. Paypal even provides one with the necessary html-code for each product so it’s almost a copy&paste solution. Though I have to admit this is only valid if one doesn’t have too many products, because the Paypal-backend is a pain to manage - or was back then.
For everything else I prefer to have the shop in a shopping software and do the content parts surrounding it in kirby.
What usually puts me of with the most solutions is besides the lack of security measurements the missing internationalisation.