Most of the sights are close together. Buy an umbrella and still go from one place to the other. Enjoy Salzburg!

My opinion, 1 day is not enough to cover both cities plus traveling time in between plus time for meal and plus time back to Vienna. Each of those cities deserve to be there at least for 1 day each. But it depends what you would like to see and visit. We enjoyed 2 full days in Salzburg (3 nights stay) and 2 full days in Hallstatt (3 nights stay) and we did everything on "high speed".

We only visited the salt mine, so I cannot compare, but between the 2, Rick Steves has a slight preference for the salt mine. We really enjoyed our tour. It was a unique experience for sure! We were in Hallstatt when it was cold and rainy and it's doable but not the best place to visit. Pretty much everything you want to see is outside and its beauty. We would have loved to rent a boat and enjoy the lake or eat outside. I was sad we missed those things!

Hello, I would do 2 to 3 days for Prague the temperature there ranges depending on the day , usual temps are anywhere from 60F to 35F . So it says !! Anyway that should be enough time to see everything, I would recommend staying near old town because walking is much easier then driving and parking. And Austria.... oh goodness there are so many great spots! Definitely recommend Hallstatt! Beautiful small town ! Vienna we had booked for 2 days and it was plenty of time to see everything we wanted to see. As you get in to the higher altitude and mountains it will be colder we were there in end of April beginning of may and there was still a chill and a bit of snow on the mountain caps . Good lunch and have a lovely time on your trip hope this helps !

Ooops my apologies, I realize I didn’t answer your question correctly :S