T-Mobile is great internationally. Free data & texting. Wait for internet if you need to call, but even that is good if you must call.
Contact your CC company & let them know your travel plans.
See what your CC offers in the way of car insurance & get a letter from them for the countries you visit.
I use CC as much as possible & choose local currency when given a choice.
We usually drive but just did a trip using the rail system through 4 countries. It was the best trip we’ve done & so relaxing. Driving internationally can be stressful.