The train from Nuremberg to Salzburg changes in Munich Hbf to Munich Hbf G1. 5-10. The connection time is 16 minutes. How long does it take a normal walker to make this connection?
What track are you arriving on? Gleis 5-10 are set back from the main platform. Upper left hand corner of this map.
https://www.img-bahn.de/s3/prod/v/img/stInfoPlan/8000261.pdf
DB estimates a 10 minute walk from Gleis 30, a set back group of tracks on the opposite side of the station, about as far away as you can get in the main station.
It is not uncommon for trains to be 5+ minutes late. And trains are not often EXACTLY on time.
If your train from N'berg is late, you could simply plan to take a subsequent train from Munich to Salzburg - as long as your 2nd train is a REGIONAL train (like the Meridian "M" train.) Jump on any subsequent regional train you like (but not the long-distance RJ train, for example.) But if you are scheduled on the RJ (or other long-distance train) to Salzburg, and your first train was on time, then you will need to catch the RJ as scheduled; if the first train was LATE, any subsequent long-distance train is OK.
Is EC a regional train?
No, EC is a Eurocity Train. International, and most certainly not regional.
The regional trains are designated "M" for Meridian and they go more or less once an hour from the Gleis 5-10 section of Munich Hbf.
The EC train means that one coach could DB, another coach could be Swiss, still another one ÖBB...all depends where it starts and ends. You have ample time to make the connection once you get off and start walking to Track 10.