I've just come back from a 6-night trip to Germany. I found Mainz and especially Heidelberg relatively quiet, minus the hordes of tourists I'm seeing mentioned here on other threads. A friend had warned me Heidelberg would be jammed, especially the Old Bridge, but it wasn't very busy at all! I arrived Sunday, the week after Easter school holidays ended, & left Heidelberg just before the May 1st holiday. Another example - I've seen pictures from a Forum friend of the Netherlands AFTER the tulips have been harvested, showing fewer crowds, little rain, and easy travel.
Wondering what other 'sweet spots' people have found, where the weather was relatively good and the crowds smaller than might have be the case?
Here's my TR -https://community.ricksteves.com/travel-forum/trip-reports/6-nights-in-germany-mainz-heidelberg-heidelberg-was-gorgeous