Hallstatt from Salzburg is at least 2hrs and 2 trains. From Königssee add another 1h15 minimum.
If you wanted to visit both from one place easier to stay in Salzburg.
How many is "WE" ???
"We will treval by train from Munich to Salzburg in May, hold eurail train pass for 3 countries (Austria, German, Italy)"
Eurail passes are often far more expensive than buying advance point to point tickets. In addition seat bookings are extra. In italy seat booking on fast intercity services is compulsory and will cost you €10 per person per journey.
Also there are local rail offers which make travelling around extremely cheap.
Here's some info regarding MUNICH, SALZBURG and local travel.
Getting from Munich to Salzburg
There is a ticket issued by Deutsche Bahn called the Bayern Ticket. For only €29 a group of up to 5 people travelling together gets unlimited use of ALL Regional transport in Bavaria for a day. Includes all city transport (e.g. in Munich), ALL Regional buses and ALL Regional trains including those services to Salzburg. Only the fast IC, ICE & RAILJET services are excluded.
Valid from 9am Weekdays (midnight weekends) until 3am the following morning. For full T&Cs see bahn.de/i/…laender-ticket.shtml and click on Bayern.
There is also a Deutsche Bahn ticket machine at Salzburg station should you wish to use a Bayern Ticket to visit places in Germany from Salzburg.
German Regional bus company RVO have bus services from Salzburg to Berchtesgaden ( ~50mins) then Berchtesgaden to Königssee & Jennerbahn (~ 15mins)
all the local services.
A day ticket for all the local buses around Berchtesgaden (including to/from Salzburg and Bad Reichenhall) is €9 per person. YOu can buy this from the bus driver on the 840 form Salzburg.
As these buses are also valid on the Bayern Ticket if there are 4 of you then you could also purchase the Bayern ticket from Salzburg station and use that.
If interested you could also use the Bayern Ticket to visit Herrenchiemsee on Lake Chiemsee (1hr from Salzburg or Munich on the Munich - Salzburg train)
or if you wish to visit Neuschwanstein from from Munich
Travelling to ITALY
Deutsche Bahn operates 5 direct Intercity services daily from Munich to Verona and 1 direct service to Venice.
The Austrians operate a number of direct coach services from Villach to Venice.
The Germans in cooperation with the Austrians are responsible for ALL cross border Intercity services to Italy from Austria. The Germans www.bahn.de and Austrians www.oebb.at cooperate on ticketting and scheduling info.
YOu can book tickets on their webiste up to 92 days in advance and therefore take advantage of discounts.
Salzburg - Venice (train via Innsbruck)
A standard ticket on the train is €83.20
even for tomorrow it is still possible to get a ticket for €49 (obviously not always guaranteed)
The same ticket booked today for the end of April for either the rail connection over Innsbruck or the faster coach connection over Villach is €29.
A standard ticket to Verona is €70 - strangley an advance purchase rail ticket to Verona was €39 - using the "Venice" service above.
If you wish to purchase through ticket to italy where you need to change to an italian service then you will not get a result online.
Also if you tried to use www.trenitalia.com for italian rail they only show the normal price not the discounted ones.