MUCH better-if you already find trains in PL ´good´ you are in for a very nice surprise.

However, the combined service between these towns is shared between OeBB=Austria and CD=CZech, both have RailJets, these differ a little in design, but not very much.

Note that 2nd cl has also family car (with some playground) and silent car-NO mobile or US-style loud talking. 1st also has a special subsection as premium-if you have 1st cl pass, you have to pay extra to sit there.

RJ is RJ, trains are all the same, incl Wien->Bp. As such all daytime trains RES is optional-but it does seem to be very busy this summer so its advisable to spend the odd € extra to do it-easiest is to simply stay a few mins longer on arrival in the station-find counter/desk and let them arrange it.

BTW- Praha is noted for its red trams and really excellent local transit-it is NOT free, even though noone will ask for tickets-best buy is a pass for 24 or 48 or 72 hrs-from machine or the tiny counter beside entry to metro in main station (hlavni nadrazi, now more disguised as a shopping centre). Seniors from any country from 70 on can travel free-just show ID/passpt when asked for tickets-except on the trains-its for bus/tram/metro.

do NOT change money IN the station-go outside for much better rates.