The OFFICial rule is that you have to '’use'’ country of residence, whichy is where you have stayed the last 6 monthes and are registrated in the public administration. However, some countries do not even have such a registration system proper. But the rules were made for EURopeans and here anyone has.
EU rail as such is better value as INTERrail-because it does not have the '’only 1 trip OUT and IN'’ in your own country. Prices hardly differ.
Also double check if a pass is even worthwhile for just these trips-this will also depend on how many breaks you intend to make and/or side-excursion trips. There is now a direct overnight train from P to Wien=Vienna and for local travel, unavoidable with your plans, in FR and even more in ES-on TGV and AVE Hi-Speed trains, cumbersome and sometimes very hard to get and costing extra REServations need to be made.