5 nights in Munich (as homebase) suggestions, relying on public transit/tour buses

If you are "really into natural beauty and the outdoors.", Munich is not a good base. Must Munich be your base?

If you are "really into natural beauty and the outdoors.", why are most of the sights you mention wanting to see towns, not "natural beauty and the outdoors."?

Pleas clarify, and then maybe we can be of help.
If you are "really into natural beauty and the outdoors.", Munich is not a good base. Must Munich be your base?

If you are "really into natural beauty and the outdoors.", why are most of the sights you mention wanting to see towns, not "natural beauty and the outdoors."?

Please clarify, and then maybe we can be of help.

Ok, let me clarify. I’m interested in the outdoors, history (Dachau/Nuremberg), nice old fashion German town (Rothenburg/Nuremberg?)
I’m not at interested in art, castles, high brow stuff.

I’m not expecting Bavaria to blow me away like Gimmelwald but I just want an authentic Bavarian experience.

If you want natural beauty, the best places on Earth that I have seen in that category were"
1) Alaska cruise and glaciers
2) Coast of Norway
3) Canadian Rockies, also, US Rockies
4) Around the Horn of South America
5) European Alps, preferably Switzerland
6) The Douro River Valley in Northern Portugal
7) New Zealand
8) Hawaii
9) The Great Ocean Highway of Australia

Bavaria is nice and can be very scenic. You might like hiking up to the top of the Zugspitze. It is a two day hike from Garmisch and amazing.

The other places you mentioned are good to visit, but not as scenic. You can use Munich as a base, but why not base in Garmisch.

Nuremburg although very nice, is a city, not really a town. Rothenburg is also nice, but in the other direction from the scenic areas. I too would suggest basing somewhere closer to the mountains. Come back to Munich a day before your return flight and see Dachau.

"Garmisch-Partenkirchen/ Zugspitze can I get around by public transit or tour bus." yes no problem. Garmisch-Partenkirchen is walkable. Other than the Zugspitze (expensive, take the train) there is the gondola to the top of the Wank and the Alpenspitz (mountains). You can also walk to the Riessersee (lake and old Olympic bobsled run) and the Kriegergedächtniskapelle (WWII remembrance chapel) and the Gasthaus nearby. There is the Partnachklamm too. I would plan an overnight in Garmisch-Partenkirchen and manager your expectations. Mittenwald and the Zugspitsarena (Lermoos, Ehrwald Austria etc.) are also accessible by train. Mittenwald might fit your expectations with the old city and painted houses. It's become touristic too, but nice and you could take the Karwendelbahn to the top for the views and a walk. Also a hike to the Lautersee and Ferchensee (lakes) is nice. I would plan at least one overnight here too, or in lieu of Garmisch-Partenkirchen.

A day trip to Nuremberg (1 hour each way on the train) is easy from Munich if you want a charming "historical" reconstructed city/churches/castles/walls/etc. Skip Rothenburg, it is too far for a day trip to see a mostly intact small city and its wall. I do love it's church though and the wooden altarpiece. If you must go there you can catch a local bus from Nurnberg (it takes about 2 hours each way) or the train (about an hour each way).

https://www.vgn.de/en/

bahn.com

Dachau takes half a day on local (S-bahn) transport and a city bus to the site (and back).

Natural Beauty and the Outdoors - Garmisch-Partenkirchen/Zugspitze and Mittenwald two hours south of Munich by train.

https://www.gapa.de/en
https://zugspitze.de/en/winter/mountain/zugspitze

In my opinion, Hallstatt is too far for a day trip - unless "outdoors" includes long long train rides and/or you have to say you have been there for two hours.

Base yourself in Garmisch Partenkirchen/Mittenwald, enjoy the many outdoor offerings and go back to Munich with a half day left for Dachau, or a day and a half left and add a day trip to Nuremberg.

You say you are interested in "natural beauty and the outdoors". I don't think Munich itself is for good that, and, with travel time, I really don't think it is good as a base. Hallstatt might be the ultimate for natural beauty and the outdoors, but it is a little difficult to get to. But a closer alternative would be Berchtesgaden, which is great for outdoor natural beauty. Maybe stay a couple of days there and enjoy it. Mittenwald is pretty, but overall not much there for the time it takes. One of my favorite places for natural beauty is Oberstdorf and the Kleinwalsertal, an Austrian valley only accessible from Germany. Spend a few days there, also. Either Berchtesgaden or Oberstdorf is about 3 hours from the Munich airport by S-Bahn and regional train. They are about 5½ hours apart by regional trains via Munich Hbf.

Another natural outdoor beauty place is the foothills of the Alps south of Munich on the rail line Bayerischer Oberlandbahn (BOB). Resort towns there are Tegernsee, Schliersee, and Bayrischzell. From Bayrischzell you can take the cable car up to the top of the Wendelstein.

I’m not at interested in art, castles, high brow stuff.

This is one of my favorite RS forum sentences ever. I love it that you own it. 👍🏻😃

I agree with those who are encouraging you to pick a base other than Munich if nature is high on your list.