I am helping a friend with her trip to Germany this May, Her and her dh will be in Germany for 12 nights. They arrive in Frankfurt and will depart from Munich to finish their trip in Barcelona. This trip is for her dh to go back and see the areas that he remembers from his time he was stationed in Germany.

I know that they will only be using trains and have lots of day trips planned while in these areas.

I did go to Man in Seat 61’s site and I have also priced out the tickets from point to point. Frankfurt airport to Hotel in city 4-nights

Frankfurt to Fulda 4- nights
day trip to Black Forest

Fulda to Grainau 4- nights

Grainau to Munich airport

I am curious about train costs. Is it better to get a Eurail pass? There is also Quer-durchs-Land-Ticket or a discount card?
What would you do?

Thanks for all your help.

Open https://int.bahn.de/en/ and study the different offers like

Super Saver Fares
Regional Offers
Travel Pass offers

and choice what suits best to your plans.

Thanks neckervd.