These OVernight NJ trains do NOT have seating in 1st cl. You can if you want a seat only use 2nd. Or-perhaps-if there are any left-book a sleeper-there are several types.

Search for the short lesson of sebastion seewulf about how best to book on the NightJet.

OR use other trains, you did not state for when, but f.e. this Easterweek many of THESE trains are fully booked Plus that there are very often works on the rails somewhere along the very long route and that means trains may also be rerouted and not serve the ´normal´ stops.

You can book this night train via ÖBB using these steps. You can sit in 2nd class with a 1st class pass.

Thanks for the helpful response.  We are traveling July 22, 23 and 27.  July 22 and 23 Paris to Krakow; July 27 Krakow to Warsaw.

The Polish trains are listed as not running every day, is this true?  It comes up as daily on the app?  Also Reservations Required.

Trip is:  Leave Paris to Mainz @ 9:06, Mainz to Wien @ 00:41, Wien to Krakow @ 11:10 arriving 16:59 on July 23.  Next leg on July 27, Krakow to Warszawa Lotnisko Chopina @ 10:01 arriving 12:58.  I’m worried about the trains into and in Poland.  Need a reservation for two of them.

Best Regards

Steve

22/7, Paris 9:06 - Mainz 13:18 (change at Mannheim Hbf ):

Paris - Mannheim: reservation mandatory. Can be done online via Eurail.

Mannheim - Mainz: reservation optional. I wouldn't bother.

23/7, Mainz Hbf 0:41 - Kraków Główny 17:07 (change at Wien Hbf and Břeclav):

Mainz Hbf - Wien Hbf: reservation mandatory, best done via ÖBB using these steps.

Wien - Břeclav: reservation optional. There are a few trains to choose from to catch the 12:10 from Břeclav.

Břeclav 12:10 - Kraków Główny: reservation mandatory. Can be done via Czech railways. Price is 75 CZK (~3.07€). You have to add the discount card Eurail Global Pass. In the results, you'll see a link "I want a reservation only”. Click on it, wait for the price to appear and then confirm.

27/7: Kraków Główny 10:01 - Warszawa Lotnisko Chopina: I see you used the rail planner app to get this timetable. Unfortunately, the timetable in the app is outdated because it doesn't get enough updates. Better is to plan with local planners (such as this one for Poland) or the German railways planner for international journeys. In addition, the Polish planner warns that there's a timetable change on 12 June and there will be changes, so it's better to check again by the beginning of June. Domestic tickets can usually only booked a month in advance, so there's no rush to get a reservation.

Eurail is not valid on the suburban trains in Warsaw, i.e. the one you would be using between Warszawa Zachodnia and Warszawa Lotnisko Chopina.