Honestly as an American, when I visited Germany I bought a deutschland ticket and used regional transit to travel most of the country. I used the DB navigator app.

It was hands down the best travel of my life. Just hop on a train and go anywhere. The delays were usually well recorded in the app and I could usually just reroute.

I was traveling for leisure though so waiting an extra 10 minutes was not a big deal, but all the city transit and local trains seemed to be mostly on time. Regional were the only ones I encountered with delays.