If you are interested in "hop-in/hop-off ticket" as you called regular tariff TCV ticket, then let us count:
Krakow-Bohumin-Breclav-Vienna-Salzburg-Innsbruck-Buchs-Zurich ticket will cost app. 135 euro. This ticket is rather easy and almost definitely cashiers in Krakow will not have any problems with issuing it, but "longer" ticket like Krakow-Vienna-Zurich-Italy would probably be puzzling to them, so it is better just to purchase second separate ticket Zurich-Milan (can be done already in Zurich) - no need to pay expensive international tariff for domestic Italian part, you just later buy Milan-Rome domestic Italian ticket. TCV ticket Zurich-Milan will cost app. 50 euro
For Rome-Paris route TCV ticket doesn't really make sense due to the huge distance, so it is easier and simpler to use domestic tickets if you plan to travel the route with multiple stops.
Resume: TCV tariff ticket is worth it only if you plan to travel with many stops in countries with high domestic tariff (like Austria, Switzerland, Germany). In your case, for the most parts of your journey you can get either discounted or relatively cheap ticket, so you need to think twice before going with TCV ticket option - count possible stopovers on the route, compare total fare with sum of discounted tickets etc.
Krakow-Vienna cheaper, but with changes: buy full regular fare ticket Krakow-Breclav (last Czech station before Austrian border), the fare is 26.6 euro, then go to
https://eshop.cd.cz/international/search_cd-obb.aspx and purchase discounted ticket Brno-Vienna for 9 euro (do it at least 3 days in advance). All the trains coming from Brno to Vienna pass through Breclav, so you just board the train there (instead of riding from the Brno) and enjoy your cheap ride to Vienna. Take a look at timetable and make sure to plan the most comfortable connection between Krakow-Breclav and Breclav-Vienna trains. Total ticket Krakow-Breclav-Vienna=35.6 euro
Other option: get off the train in Breclav and simply buy full ticket Breclav-Vienna for the next train, costs app. 20 euro.
Regular full fare Krakow-Vienna is app. 60 euro, so with first option you save 25 euro, with second one - 15 euro. All these with minimal time loss. Remember to try to purchase discounted Krakow-Vienna ticket first, then you will not need all those tricks