Is a guide helpful for Rothenburg ob der Tauber?

I would say no, not that helpful. The RS guidebook is very helpful. It is a small town. You can learn a lot just taking the Night Watchman Tour.

We've visited there twice, and found the info in the RS guidebook sufficient for our needs. And the Night Watchman tour is a must do IMO.

I definitely agree with the recommendation to take the Night Watchman tour. He is awesome and the town is so charming to just explore on your own before and/or after that.

info on that tour - https://duckduckgo.com/?t=ffab&q=Rothenburg+night+watchman&ia=videos&iax=videos