Mag, hoeft niet, tenzij je perse in de nachtrein/slaapwagen wil. Wel aanbevelenswaard als je niet de stoelendans in de enige doorlopende trein ICE wilt.

With ICE via Germany not, only optional. Bookable via bahn.com (4€/journey) or ÖBB seat only (3€/train)

With the nighttrain Nightjet (in couchette and sleeping car) yes, bookable via tickets.oebb.at - one way ticket - discount: Interrail/Eurail Globalpass

With the seat cars of the nighttrain that run as Intercity, only optional reservation. via bahn.com (4€/journey) or ÖBB seat only (3€/train)

Via Paris Thalys needs reservation and also TGV to Switzerland.