With the pass you can select on your own which trains you wanna catch :)
Most Nighttrains need a reservation means you have to reserve your prefered comfort level before you catch a Nighttrain :)
How ever the Nighttrain Paris - Venice doesnt exist anymore :) Current otherway could be a TGV/ICE from Paris to Stuttgart and catch the Stuttgart - Venice Nighttrain :)
Other Nighttrains you may use are Paris - Vienna, Amsterdam - Innsbruck, Prague - Zürich.
The Nighttrains Stuttgart - Venice, Venice - Vienna, Vienna - Berlin, Berlin - Zürich are all operated by Austrian Rail under the brand of Nightjet :) you can book (ticket & reservations) or reserve (just a reservation on top of a Interrailpass) easily on the website of oebb.at :)