Trains between cities

You buy tickets from your start point to your destination. But to go from Nuremberg to Rothenburg, you actually buy a VGN ticket. that stands for Verkerhrsverbund Grossraum Nuernberg, aka Greater Nuremberg Transit Authority. You can buy it out of a ticket machine.

And why not go like this; RE 90 to Ansbach, then RE 80 to Streinach, then the RB 82 to Rothenburg. Takes an hour and 15 minutes.

Munich-Nürnberg: Compare (saver) fares for the ICE with the price of a Bayern Ticket (good for regional trains only). The fastest regional train, line RE 1, taks just half an hour longer.

Nürnberg: The VGN day ticket ("Tagesticket Plus") mentioned by Sam covers you for Saturday and Sunday, so buy that already on Saturday and not an extra day ticket for urban transport. You need a ticket "Preistufe 10" (price level 10). Buy it at a ticket machine in the main station or at any U-Bahn station (most can be set to English).

Rothenburg-Würzburg: A Bayernticket for two is slightly cheaper than two standard fare tickets, but one standard fare ticket is cheaper than a Bayern for one. NB. There is no need to validate a Bayern Ticket.

"...does the machine give out 3 different tickets or just one ticket that I validate once on the first train?"

The VGN Ticket which Sam refers to is issued by the local transit authority (VGN) which handles all "local" means of transportation (called Nahverkehr in German) for journeys within its very large territory:

https://images.gutefrage.net/media/fragen-antworten/bilder/459443150/0_full.jplog?v=1655930239000

The only journey you mention that lies fully within the VGN is Nuremberg > Rothenburg. A VGN ticket can be bought at a station ticket machine or using a VGN or DB app for any trip inside the VGN. Your one ticket will cover ALL changes of train necessary for your journey as long as you are riding the regional (Nahverkehr) trains. A VGN ticket covers more than trains... If you are staying some distance from the Nuremberg train station, somewhere in the old-town zone by the Kaiserburg for example...no worries... The exact same VGN ticket will cover a bus ride or a subway ride to the station as well, and you can buy it from a machine at the subway station or from the bus driver; it will cover the bus or subway ride plus all the trains you need that day too. In Germany, the 3 regional trains you will use to reach Rothenburg are looked at as mere extensions of a local bus ride, so ticketing is streamlined. No reservations. Seamless.

And you do not validate these tickets. A VGN point-to-point ticket is already time-stamped upon issue and expires after some set period of time. Use it immediately. Or you can buy a VGN day pass (Tagesticket Plus, for example) which is flexible for your date of travel - use it at any hour. This day pass can be pre-purchased for a specific travel date for convenience.

The number of trips you are plannning make you a good candidate for the Deutschlandticket (€49/mo.) which will eliminate the need to buy separate tickets day by day. You could use it also for the Munich > Nuremberg trip and the Erfurt > Frankurt journeys as long as you ride only the regional trains on these routes. One ticket for everything... or you could pre-purchase a DB saver fare ticket for one or both of these two routes in addition to the D-Ticket.

Thanks for your imput.

Sam: yes the route you mention is listed on the Deutsche Bahn website; it's looks better than the route I mentioned that I got from Google maps.

I am thinking I will buy two ICE tickets for my first and last major train trips in advance and then at the last minute I will just buy tickets for my other trips from the machines. If the monthly ticket is for a calendar month, considering I will be in Germany during 2 calendar months, part of August and part of September, I doubt i want a monthly ticket.

Does a ticket from Nuremberg to Rothenberg ob der Tauber say which specific trains to take, or is it just for a certain amount of time worth of train travel on any trains and then it's up to me to check the Deutsche Bahn website and pick which trains I will take? (Hopefully I would find or pick the route that makes most logistical or rational sense if there is more than one choice) (It's all probably simpler than i think but in Michigan we don't have commuter trains and most people drive everywhere and the buses are mainly just used by the disabled and super poor and the few who don't or can't drive or can't get a ride).

If you buy a one-way VGN price level 10 ticket, it is good for 6 hours. If you are traveling with someone else, you can buy a day ticket good for the entire day in the VGN network for a bit less than 2 one-way tickets.

This will be a solo trip.

Still, for the trip Nürnberg - Rothenburg, a Tagesticket Plus (€23,90) will be slightly cheaper and way more flexible than two single tickets à €13.42.

"Still, for the trip Nürnberg - Rothenburg, a Tagesticket Plus (€23,90) will be slightly cheaper and way more flexible than two single tickets à €13.42."

Why would there be such a thing as two single tickets, because this is actually a solo trip? And I thought I had figured out that one person buys just one ticket for one trip, like one trip is bought as a single ticket even if the trip involves more than one train or transferring to a second or 3rd train.

My research from checking for trips on the Deutsche Bahn site seem to be, and my interpolation of replies here is, I don't have to buy any tickets in advance; trips involving various kinds of commuter trains only can't be bought in advance; trips involving only an ICE train or an ICE train and local train(s) can be bought in advance, which might save some money, the exact amount I would save is unknowable; ICE trains can sell out or the prices rise at the last minute; local trains never sell out, even if you have to stand on the trains.

I have no opinion about flexibility versus just making myself arrive at the train on a ticket before the given time it leaves. I didn't find a list of prices for Tagestickets.

If you can show up for work on time, you can show up for a train at the time on a ticket you bought in advance.

Should I buy tickets in advance if I can or just skip buying any tickets until the last minute when I get to the train stations?

only an ICE train or an ICE train and local train(s) can be bought in advance, which might save some money, the exact amount I would save is unknowable

It is totally knowable. Just compare the price of a Super Sparpreis ticket bought now for your date of travel vs the Flex price.

Yes, we get you are traveling solo, so we'll just table all that group ticket chatter. The trip to Rothenburg is one way and you are staying overnight, then moving on the next day.

Why would there be such a thing as two single tickets, because this is actually a solo trip?

I misread your first post and thought you wanted to travel back to Nuremberg on the same day. In that case, you would have needed the other single ticket because the VGN doesn't sell return tickets. Please accept my apologies. So you actually need the VGN ticket price level 10 mentioned above.