Would Love Some Feedback on Tentative Plans Bavaria

Your whole tour is more comfortable to do by train - with the exception of Lichtenstein.
From MUC airport to the city there is an S-Bahn every 10 minutes. The journey to Salzburg by car is not faster than by train and parking is expensive (and at the moment you still need a vignette for the short stretch from the border to the motorway exit Salzburg, but that will change soon). Parking space in Dachau is limited and travelling by S-Bahn and bus is more comfortable. In Stuttgart, Strasbourg and even Nuremberg a car is more of a hindrance than a help. I'd limit the car rental to the day trip to Lichtenstein (or replace it by another destination, e.g. Tübingen, which offers a lot of historistic 19th century buildings too).

"Would Love Some Feedback..."

"We are sticking to Bavaria, and a possible overnight to Strasbourg, France."

Bavaria is quite large, but it doesn't include Stuttgart or Ludwigsburg. With the vast number of palaces and other nice places to visit in Bavaria, I don't know that you gain much at all with this lengthy driving trip to Stuttgart and Strasbourg - I think sticking to Bavaria is a sound idea. If Strasbourg isn't a must (and it's not IMHO) then I'd abandon that Sat-Mon detour in favor of more time in similar places much closer to Nuremberg and Rothenburg. Please see suggestions below.

Würzburg and Residenz Palace - the palace is a UNESCO World Heritage site

https://www.ricksteves.com/watch-read-listen/read/articles/wunderbares-wuerzburg

Bamberg (also UNESCO WH)

Walled town of Iphofen (between Nuremberg and Würzburg)

Bad Windsheim's Freilandmuseum (not far from Rothenburg.)

"2)If I get a rental at airport, is it feasible or more work to drive, find parking, etc in Salzburg and Dachau?"

More work. Same is true for Stuttgart, Strasbourg, Nuremberg, big places where cars are a pain.

I would use the trains exclusively for ALL your stated destinations, or for Bavaria-only destinations as I suggested.

Hypotheticals based on my suggestions above:

Munich > Salzburg > Munich: Bayern Ticket day pass (€32/2/day.)

Day trip to Dachau: Use local MVV transport, usually S-bahn + shuttle to the camp. Cheap.

Munich > Nuremberg by train on a Bayern Ticket day pass (€32/2.) Includes transport within the two cities. (Note that you could visit Regensburg for most of a day on the way to Nuremberg for no extra charge!)

Base yourselves in Nuremberg and day trip out to Bamberg, Rothenburg, Iphofen, Bad Windsheim: a €20 day pass gets you there and back on each day (VGN Tagesticket Plus.)

Nuremberg > Würzburg day trip: Bayern Ticket again.

You don't want to stop mid day to see Rothenburg ob der Tauber. You want the opposite. Spend the night and see it morning and late/afternoon evening. Otherwise it is mobbed with day trippers. We did that and it was like someone flipped a switch around 4 pm and again at 10 am. Between those hours it was heavenly, otherwise it was a zoo.

We visited Bamburg and Regensburg by train as day trip from Nurnburg where we based for several days. That plan worked well for us.

Thank you all for your feedback!! I definitely will look into trains for transportation then. And thank you for the other options listed, I will look into!

Taking tours to get a feel for the city....
I find that Rick's books provide the absolute best self-guided tours. I like to tear out the section of the book and roll it up to fit in my pocket so I look less like a tourist. We did Munich as guests on a RS tour group. Our guide (Daniel) was fantastic, and he did the exact tour (minus Michael Jackson memorial) that was in the RS book.

I suggest to either use one of the guides RS recommends or the self-guided tour in the book rather than some random guide of your choice.

If you do decide to go to Stuttgart, I'd advise visiting Esslingen over Ludwigsburg. We were very underwhelmed by Ludwigsburg, and many rooms of the palace are under renovation; the gardens won't be doing much in March-April.
Enjoy your trip and safe travels!