1st Class Benefits:
Individually adjustable seats
More room between the seats sideways
Extra wide tables
Electric outlet per seat
Cabin service: menus are served at your seat
2nd Class Tickets are;
Modern seats in open cars
Compartments (6 seats)
Generous luggage racks / luggage compartments
One electric outlet per double seat
Restaurant and bistro car
Wi-Fi (Some cars)
That looks like some text I saw on on the Eurail website. And as much of the Eurail pass website, it is carefully crafted near-truth designed to mislead the novice traveller without actually lying.
It cannot possibly be true, because Eurail doesn't run any trains. The trains are run by many many (probably nearly 100) different railway companies in different countries. And each company buys its own trains, different models for long distance trains to those used for shorter runs, and of different ages from brand new to 30 years old.
It is about as factual as saying cars running on US roads have GPS fitted.
2nd class is 2+2 seating, 1st class is 2+1, with a little bit more legroom. Seats may be "airline style" (facing back of set in front), or the more traditional facing front to front. Most coaches have a mixture. Whether WiFi, electrical sockets, buffet and other facilities exist depends on the policies of each rail company a lot more than on 1st/2nd class.
If you want to see what the trains are like, go to the "Man in Seat 61" website ( https://www.seat61.com/ ), and select the section for the country you will be travelling in.
Note this site separately describes the trains in each country on different webpages, because there are significantly different.
Sorry for the rant, but the Eurail website needs very careful reading if you are not to get the wrong impressionism.