car rental in munich

whichever you get you must tell them which countries you are going into - different cars won't be allowed into certain countries

Whichever is cheapest for the car you want. We often use Sixt, but just check pricing.

I doubt there’s any restrictions for Czechia. I know there isn’t for Austria other than you have to buy a window sticker (vignette) at a gas station near the border.

Some rental companies may have stricter rules, but I’d be surprised if there was an issue.

Any reason for the car outside of Bavaria? Especially driving to Prague seems like an unnecessarily expensive and clunky option on the surface

Munich to Prague you can drive north from Munich along A9-A93 to the intersection with A6 (1.5-hours), then east along A6 and E50 into Prague (2.5-3 hours). So probably an overnight. You will need a vignette for the Czechia Autobahn. You can get that at the first rest stop in Czechia. 10 days for 310 Koruna. No more vignette sticker, you fill out an application form with the cars license plate. Parking in Prague can be challenging. I used to park at the main train station, but now that area is used for rental cars. Last time I used Parking Center, Wilsonova 372/6, 110 00 Praha 1-Vinohrady. Not far from Wenceslas Square. I highly suggest a good Navi that you are familiar with. Many street trams in Prague too.

Is the idea to stop off at Pilsen or somewhere along the way? I’m scratching my head about driving.

Probably going to stop in pilsen a few hours, then 2 nights in prague and 1 in cesky krumlov and the 2 in salzburs and 3 in fussen germany, The hotels have parking for about $10 a night. Some of the sights, like europcar have higher insurane rates. Can we get Allianz ins first.

I assume all the gps in the rental cars will have English. Does renting the gps also include using it for phone service in Europe?

Your gps is just your satnav. You’ll need to either pay for some sort of international plan w your current carrier (eg AT&T charges you $10/day) or get a SIM card/eSIM for your current (unlocked) phone or buy a burner phone. There are lots of threads here and other websites that do a better job explaining this. But bottom line, the GPS is just for navigation.

And yes, your GPS will almost certainly have English as an option

There are parking areas outside of the old city part of Cesky Krumlov, but just about zero inside other than a few residents. If you haven't yet, ask for parking when booking a hotel there. I parked at Parkplatz P1 am Schloss. It's been a few years, but I visited and parked at the Pilsener Urquell Brewery in Pilsen and walked from there into the old city.

Don’t assume the car’s GPS will be in English. The language will need to be changed. Kinda hard to do if you don’t speak German. We made that mistake once. We learned pretty quick how to say “turn right”, “turn left” in German. Never could figure out how to change the language, we just followed the map. For a 3 week trip.

And GPS has nothing to do with your phone. You won’t get any phone data if you pay for GPS.