Moving around by train....
 

So we're headed to Munich and then will have stays in Salzburg and Nuremberg as well. We will also use the train for days trips to places like Regensburg, maybe Wurzburg or any other places of interest we may learn about. Is one site any better than the others to buy tickets? Should we bother with the Bahn Pass? For what it's worth, I plan on booking First Class tickets from Munich to Salzburg and then from Salzburg to Munich. I'm not concerned about the other routes as they will be rather short.

Yes, there is a better site - www.bahn.de (www.bahn.com). Buy directly from Deutsche Bahn, and they will not add anything to the purchase price. In addition you can use the site to search for trains in nearby Austria (Salzburg), or even trips literally door to door.

I am not sure whether by Bahn Pass you mean a rail pass, or a BahnCard. Rail passes can be convenient but not always cheaper. You would have to add up your point-to-point tickets and compare with the price of a rail pass. A BahnCard usually only repays itself if you live in Germany and use it frequently. It is also a subscription, so if you did get a BahnCard you would have to remember to cancel it. It's not really designed for tourists.

Good luck, sounds like a great trip!

Lavandula

May be you check https://int.bahn.de/en/offers/region...ticket-bavaria too.
All depends on the nature of trains you plan to take.