Lübeck is a natural on the way to Berlin, as is Tangermunde.


Somewhat out of the way toward Düsseldorf is Lüneburg:


For scenic routes while driving, avoid the autobahn and choose roads going through forests.

A few years ago we followed the Brick Gothic Route from Lüneburg to Parchim. That was quite interesting. Then we drove west across the country from Wismar to Düsseldorf stopping the whole way at Christmas markets (Wismar - Parchim - Schwerin - Hildesheim - Hameln - Münster - Düsseldorf - Aachen - Masstricht - Brussels). It was an interesting trip and while the Brick Gothic thing was not so interesting by the time we got to Parchim, it was a good drive through some interesting scenery. The western side of the route is better kept than the houses and fields to the east. Google it, there is a lot of information on it which wasn't there at the time we did our drive.
https://www.germany.travel/en/leisur...ck-gothic.html

Another drive you might contemplate is doing part of the Fairy Tale Route which stops at all the Brothers Grimm sites between Bremen and Kassel or thereabouts.
https://www.deutsche-maerchenstrasse.com/en/
We have done a few of the stops and it's quite good. You have the added fun of reading up on the stories before you go!

Lavandula

As for scenic drives get Michelin Green Guide to Germany as it highlights in colors really scenic and scenic roads. And the drive up to the Brocken, a famous mountain resort could be on the way and also thru cute cities like Celle, Goslar ad more.