Yes they're pretty much all included. You only need to pay accommodation so often about 10-15€ for a seat, 30€ for a couchette and 60-100€ for a sleeper. It depends a bit on the route too.

Night trains are very popular so book well in advance. Most of the summer is already sold out on some routes. For most routes use nightjet.com or tickets.oebb.at (add Interrail as a discount).

Here is a nice map showing all European night trains : https://back-on-track.eu/night-train-map/