Might need to rent a car to drive across multiple countries in Central Europe and Scandinavia.
Are there any special tips to take notice when looking for rentals? Will this be compatible with most major rental companies (Europcar, Sixt, Hertz, Budget, whatever)....without, obviously, having to ask each rental office individually?

I know many car rental put special restriction on certain riskier countries e.g. Belarus, Bosnia and Herzegovina, etc, but I figure for traversing through the rest of the continent it should be okay without asking for permission explicitly.

Also I know to make sure that proper tires are equipped for condition, and be aware of tolls and vignettes requirement. Just didnt know if there is a special checkbox required when searching for cars for such a trip