Train Route from Ljubljana to Vienna?

The RailJet departing Villach is Austria's newest, fanciest class of train and should be plenty comfortable. No issue with booking SparSchiene discount tickets as long as you are committed to this travel date and time; consider them to be nonrefundable and nonchangable (there may be some allowances but I'm not looking at the ticket details).

I have not traveled from Ljlubljana to Vienna, but have taken the train between Graz and Vienna many times over the past two decades. It is a scenic route that goes through the Semmering. There are no gimmicks with the SparSchiene tickets; I recently bought deeply discounted tickets on-line from ÖBB for three upcoming rail trips, including Graz to Vienna (on a Railjet), and have also bought them in the past. As for refunds, the following is from the ÖBB website: (1) For SparSchiene Austria: "The number of tickets is limited. Exchanges and refunds are not allowed." (2) For SparSchiene Europe: "There is no refund for ÖBB SparSchiene Europe tickets for Nachtreisezüge (EN) and ÖBB Intercity buses. Other ÖBB SparSchiene Europe tickets may be refunded up to one day before the first travel date with a deduction of 29 Euros per person and direction. From the first travel date onwards, a refund is no longer possible." I would assume since your trip starts in Slovenia that the latter might apply. But either way, if you miss your train on the travel day you eat the cost of the tickets. The bottom line is if you can commit to a specific train, they are quite worth it. You can also reserve seats. But SparSchiene tickets are limited, so the earlier you book, the better the chance that they will be available for a particular train. I believe that you can book 6 months ahead.