I ran GrapheneOS on a pixel 5 but ultimately went back to stock.
GrapheneOS was considerably slower on my phone. Apps took a bit longer to loader, but the worst was installing APKs, it takes so much longer compared to stock. Some apps (e.g. revolut) took more than 5 minutes to install, it was crazy.
In Europe I would say debit cards are way more common than credit cards. It's very rare to see someone paying with a credit card.