Upvote:2
While my experience is in the US, I'd say that it's generally a good idea to have cards for where you think you'll end up needing to charge, particularly if the station is in an area with poor mobile coverage and you can't remote start with an app. Some networks have virtual RFID cards, which will be helpful where you don't have data coverage.
If you're renting a car, I'd have a plan on where to charge depending on where you think you're going to go. If you own the car, then it's a good idea to figure out places where you can routinely charge.
Upvote:2
Yes, it is wise bring multiple cards. Sometimes cards work where apps don't, and sometimes one card works but another doesn't. My experience in Germany and The Netherlands in April 2022:
I had registered with three mobility service providers (Maingau Energie, Plugsurfing, and Shell Recharge). For the latter two, I had ordered RFID cards. For Maingau I had only the app. My experiences after charging five times, each time with a different charge point operator: