The Deutschland ticket is of no use to travel between cities. It includes regional trains but a regional train only goes from the city to it's surrounding suburbs (the train from CDG to Paris is a regional train for example).

​​​​​​Nowadays you can buy in advance point to point train tickets at a significant discount.

The rail pass is hundreds of dollars and it is not a real pass as you just don't hop a train with the pass and go .it requires reservations and good luck getting on the train you specifically want. It's kind of a scam if you ask me.