As I've mentioned in the OP, I've been to the BMW museum, although that was in 2012; worth a refresh? Not terribly interested in the Crown Jewels, to be honest. I'd rather do things outside than go to museums (save for that technology one).

Great list, thank you! Let's see...
I keep hearing about Residenz, but I am not quite sure I'm in the mood for it this time 'round. I hate to sound uncultured, but to me a visit to a place like this requires a bit of intellectual investment (preceded by a bit of research so that I know what I'm looking at) and I honestly don't have the mental capacity for that right now.
If the weather complies, this could be worth a stop. I'm not a huge beer drinker, but it looks fun.
Very high likelihood of that.
Ettal might be worth it for the cheese alone, since the same thing said about Residenz would likely apply to the cultural and historical aspect of the monasteries themselves.
This actually might be a possibility from looking at the photos of the grounds. Plus, if it's close to Ettal, that's a bonus.
High likelihood of these, as well.

I'm going to start whittling the list down tomorrow and hopefully come up with a tentative itinerary by the end of the weekend:).

Right, then. I am thinking of this as my first draft (highlighting the important questions/stops for those who don't like reading long posts):

4/28: Throwaway day that I don't want to throw away - I usually just power through the first day to fight off jet lag, plus I might sleep on the train. By the way - is there much difference between the two classes on the ICE? Could use a couple of recommendations about some nice cafes close to city center, as well. Or I might just go to Augustiner-Keller for late lunch/early dinner. If I have the energy and the sun is still up (sunset is around 6 pm), I might even go plane spotting then.

4/29: Deutsches Museum in the morning (opens at 9 and I'm going to be wide awake around 6, I'm sure), visit the Viktualienmarkt around lunchtime, then pick up a car and be on my way. As the museum in Dachau is open until 5 and the drive is short, I could go then. I'm sure I won't last more than two hours, but I kind of feel like I need to do this, even if it is for a short visit. Then drive to Regensburg for the night. That's about 150 km, all told.

4/30: Explore Regensburg and maybe Weltenburg. In any event, Rothenburg ob der Tauber would be my destination. Should be an easy enough drive to make in about three hours. (250 km, if I'm rounding up).

5/1: Feels like there's more to do and see in Rothenburg than Regensburg, but I still don't think it would hold my attention until later than mid-afternoon. The drive to Garmisch-Partenkirchen is a bit longer (300 km), but I should still be able to make it in four hours or so. Could use advice on where to stop on the way. Maybe Ulm? There's a bread museum there..:D

5/2-5/3: As Garmisch, Mittenwald, Oberammergau, Ettal and (maybe) Schloss Linderhof are all covered by less than 100 km and I'll have a full two days to explore, all I need now is to figure out how to organize my time around them and when to go to one of Tegernsee or Berchtesgaden (weather permitting, of course). That's 200 km or so (including the return trip to Munich) with Tegernsee, 400 with Berchtesgaden.

How's that? Keeps me well under the km limit even on the long side (900/1,100 overall, so even with a side trip or two I should be OK) and covers what feels like a lot while leaving a bit of wiggle room at the end of the journey. I'm usually not one to hang around the same place for too long, so it's very much in character for me to travel this way, but still if you feel like this may be overkill and I can skip something, I'm all ears. If the route itself sounds OK, it would be nice to know of any local attractions (not just food-related) that you've been to/seen/tried.

Of course, another option would be to do a different loop and go to the Bavarian Forest National Park, Ceske Budejovice and Linz, but something tells me this is best left for another trip.

In my opinion not much difference. You have more space in First and you can order drinks and food at your seat without the need to get up. First is usually quieter than Second due to the fact that there normally less people in First.

Be advised May 1st is Labour Day in Germany and a public holiday. Check if the things you would like to see are actually open.

Good description. In my opinion seats in First are much better. Often First is only slightly more expensive so it would be a no-brainer for me. If price-difference is significant especially on short trips second class should be the wiser option.

Good shout. I don't think it should be too big a problem, though. If the bread museum is closed, I don't think I'll lose too much sleep over it:).

The difference is 20 Euro, if memory serves. Might actually be worth it if I'm in with any kind of shout of sleeping. I seem to remember (from a 2005 trip, granted) there being closed compartments on some German trains in first class, but I'm not sure those were ICE...

Yep, just checked, closed compartments are, indeed, a thing. Looks like it's going to be worth the investment.

Normally you can choose between Abteil (closed compartments) and Großraumwagen (Open seats). Also possible in second class. Closed compartments are not necessarily more silent. Once I did a business-trip to Hamburg and had 4 bald eagles in my First class closed compartment. Horror! They talked all the time and exchanged "Butterbrote". Also don't like the 3 seats row. Normally I take a single seat at the First class Großraumwagen.

20 € should be worth it in every case.

I must admit, the bald eagles and butterbrote flew (no pun intended) a bit over my head, but yeah, I'm convinced it's worth it:).

also you get access to their first class lounges in many big stations..

Which airport are you coming from, since to mention the train..
spotting is an option..but check the flights table first..there are some dead times...and you will not see a lot..do you know the spotter places?
Far too short for Deutsches Museum...the main building needs about 2 days to see all of it (whats your favourites?), then, since you are into aircrafts, it has separate aircraft museum http://www.deutsches-museum.de/en/fl...r-information/ in Oberschleissheim (25 min by car from the museum) which is definitely worth seeing and the third part is the transport museum http://www.deutsches-museum.de/en/ve...ation/concept/ with cars and trams etc. about 10min drive from the museum. You can buy a combined ticket and visit the three museums on different days..
Going to Dachau is surely worth it and Regensburg is nice too..take a night walk there..
Exploring on a Sunday...well..I prefer Regensburg with open shops ;)
Weltenburg is great, but can be crowdy on a sunday, especially if the weather is great and the beergarden is open..
To be honest..I would skip Rothenburg.. far too touristy and crowdy..and since its May1st, could be that all shops and touristy places are closed..At least check that out first with their tourist office before going..
Driving down to Garmisch on that day should be easy peasy..no lorries on the Autobahn..Ulm cathedral is worth to look at..tallest church tower in the world
There is a great panaramic road near Berchtesgaden.well worth it if the weather is great http://www.rossfeldpanoramastrasse.de/en/
but even driving from Garmisch towards Berchtesgaden is great..if you know where to drive

the whole trip seems overloaded...to much road..less enjoyment of the nature and scenery..
where are your hotels? Munich and Regensburg?

I'd likely be driving. Good point about dead times; as far as the places go, I read about the museum and a park next to it? Might be worth a refresh.
Hmmmm... Although I am usually not much one to stick around one place for too long (museums included), there's a lot of cool stuff here. I might have to re-think my strategy.Yeah, that definitely does concern me. I've been to Switzerland before on a holiday and everything was closed, down to the sandwich shops. This might push me to re-think this entire loop and go south rather than north, to be honest. At least in nature there's not much risk of having too many things closed:).That's good to know. Tips always welcome;).I like driving. That, in and of itself is enjoyment for me, especially if there are nice places to see on the B-roads. My hotels would be in each of the cities/towns I'd mentioned.

I think I'll just stick to Verkehrszentrum. Otherwise it might be overkill:).

Lots of good suggestion here I don't think I can contribute anymore...

But not sure if you're a car person but you can rent a car at BMW Welt for few hours or even overnight! Last time I was there was 2015 and I rented the M6! I wanted to rent the i8 but it was fully booked :(. But the M6 was still nice, was able to do 210km/h! :) could have gone faster but its Munich autobahn can be busy, plus some parts had a speed limit.

The Marienplatz is their Square where the Neues Rathaus and St. Peter's Church.

Also Hofbräuhaus is a traditional tourist place, even if you don’t like to drink beer their food is still very good!

If you drive to Salzburg, you can check out the house of the Von Trapp family from the Sound of Music.

Very much so. In fact, this entire trip is partially predicated on renting whatever hot hatches I can find in Avis's, Europcar's and Sixt's fleets:). Also, Nurburgring and Spa Francorchamps.If they have M2s, I might be interested. Sixt does, but they also have an A45 AMG for the same price and splitting a rental into two would be too expensive, so I'd have to pick one or the other and I've wanted to drive the Merc for a while. But if I could take an M2 for a spin for a couple of hours, it would be a nice bonus.

EDIT: looks like they don't have an M2 - just an M235i and an M135i (sadly, both automatics). Not worth it for 135 Euro/3 hours when, if I really want to drive an M2, I can just book a second Sixt car for less than that for an entire day. Still, it's a neat option I didn't know about.I've been. Not a huge fan, tbh. Felt more like a traditional tourist trap to me.Noted, but not really my thing:).