First timers visiting Germany from New York in spring '22. After visiting friends in Sankt Martin/Edenkoben (45 mins west of Heidelberg), our plan is to spend 3-4 days traveling en route to Munich. Is Strasbourg and Baden Baden worth a visit? What are must sees? We will be renting a car out of Heidelberg and could keep it thru Munich or drop off and train to Munich.
Strasbourg is in France - might as well stick to Germany with so little time. Perhaps your friends will have suggestions for you in the immediate vicinity. But when you leave, you don't have to go far to find delightful places. Suggest you check out these places... they are not prominent in Rick Steves but tend to be very popular with Germans themselves.
Speyer has several big draws.
Southeast of Heidelberg on the Neckar River and in the direction of Stuttgart is the old-world wine town of Besigheim.
Esslingen is on the other side of Stuttgart, also an exceptional place to visit.
I'm not so keen on Baden-Baden but those who enjoy casinos and spa treatments might be. Nearby Calw in the Black Forest, and the University town of Tübingen, also in the orbit of Stuttgart, are terrific.
I'd skip B-B too. Ulm (for their cathedral) and Augsburg are nice enough towns, with history and architecture. But if it were my first time, I'd head for Garmisch-Partenkirchen which is in the alps at the foot of the Zugspitze. Second choice would be Lindau on the Bodensee. With 3-4 days you dont have much time for stops along the way, so I'd ditch the car and use the train. All these places are accessible (center to center) by train.
I enjoyed Strasbourg for the very limited time I was there and would have liked a few more hours there. Yes it is in France, but it’s right on the border and not out of the way. Covid restrictions between countries could be a factor, but it wouldn’t be hard to find an alternate place if you couldn’t cross the border.
I find Munich overrated. But the mountains nearby are not overrated. If there are performances on the Seebuhne in Bregenz, Austria, I would detour for that.
I would go south. Down to Freiburg / Schwarzwald, Lake Constance / Lindau, and then via Oberstdorf / Füssen (Neuschwanstein) / Garmisch-Partenkirchen up to Munich.
I think Strasbourg is always worth it, but it has my favorite church so I'm biased.
With a car leaving Heidelberg you could follow the Neckar, this is a route often overlooked by international tourists but is a beautiful and traditional wine area. It's worth at least a half day since you're already up there for the scenery alone, more if you like wine.
I heartily second the recommendation for Esslingen and Tübingen, real hidden gems for international tourism as well. Esslingen was a Free Imperial City of the Holy Roman Empire and the old town survived thr war almost entirely, it's over 1300 years old and you can even see subterranean church ruins from that period as part of a guided tour from the city.
If you are interested at all in cars the Mercedes Museum in Stuttgart is probably the best auto museum in the world, and the free factory tours at their plant in Sindelfingen (must be arranged in advance) are great, too.
It's also hard to go wrong with the Bodensee (Lindau is my favorite town there, Meersburg is also charming) and the Schwäbisch Alb is a beautiful region with castles, cheesemakers, and hiking inbetween.