From Paris to Salzburg, then to Vienna

It's hard to make rail passes pay these days and it would be particularly difficult for only two legs of travel. I don't see a Euronight directly from Paris to Salzburg, but there is a CNL night train from Paris at 20:20 to Munich at 7:16 with a connection by RailJet from Munich to Salzburg. You could get special low fares (€99/P in Eco Dbl) with advance purchase for this connection (if you book it as the CNL train to Munich and an RE to Freilassing, which is right across the river from Salzburg). You can find these connections, along with fares, on the German Rail website.

Thank you very much for the advice. I also have another question about the passes. If I purchase an One Country Pass for Austria from OeBB, what type of trains can it be applied to? Because I am planning on spending the least amount of time on traveling between each cities. Thank you again.

I think that with any kind of pass, you can ride all of the trains in Austria. Unless specified otherwise, express trains like ÖIC and ÖEC do not require reservations, although optional reservations might be recommended and will be nominally priced. I think some classes of service (but not all) on RailJet require payment of a passholder supplement. With advance purchase on the OeBB website, you can get a date/train specific RailJet or IC/EC ticket from Salzburg to Wien for as little as €19.

Passes in second class on RailJet require no supplements, no reservations required either. Can't speak for first or super premium superfirst.

I believe first class is covered with a first class rail pass, so they must get extra money for super premium somewhere, probably by charging a premium to use it. Up date: According to the Eurail website, the cost of an upgrade to Premium class on RailJet is €25.