Travel itinerary is a planned for Aug 2017 and suggestion welcome:
Fly Copenhagen Denmark to Warsaw
Train Warsaw - Prague
Train Prague -Vienna
Train Vienna - Salzburg
Fly Salzburg -Munich
Trains are OK where mentioned? All trains are priced equally? Is there only one train service?
Temperatures seem to be high 70's-low 50's.

How much time do you have for this trip? Please count the number of nights you will have on the ground in Europe. Lay out your plan on a calendar, showing you how many full days you will have in each place. It takes 3 nights somewhere to get two full days. You can't count your travel days as being days in a place to sightsee - you'll spend much of the day getting from one place to the other. Count from checking out of lodgings in one place (then transport to the train station, waiting time, actual transit time, getting to your lodgings in the next city, getting checked in and settled). IMO any place that is worth visiting is worth at least three full days to explore - meaning 4 nights. You have 6 destinations listed.

For info on trains, look at www.seat61.com

Train from Salzburg to Munich is easier and takes less time than flying if you count security etc. Unless you have a connecting flight at Munich Flughafen...

Have a great trip!!!

Temp will be between 20 and 30 c

The master guide to all things railroad: www.seat61.com
It will show that most trains are run by national government agencies (but not all) and that prices on many major routes (but not all) can vary according to the schedules and how early the ticket is purchased.
To compare Europe's budget airlines: www.skyscanner.com

> Train from Salzburg to Munich is easier and takes less time than flying if you count security etc

There are no flights between Salzburg and Munich. It's a 1:30 to 1:50 train trip.

It's impossible to answer this question when all you have given us is a list of places you'll take the train from and to. How many days (excluding the first and last travel days) do you have in total for this trip, and how many nights do you plan to spend at each destination?

No, the price for every train ride is different and depends on the distance, the type of train, the country of origin, and how far in advance you make your bookings.