On the Eurail timetable InterCity trains appear as "IC". InterCity buses do appear in the timetable, but without an abbreviation. Reservations are required for InterCity buses. For InterCity trains an advanced reservation is not necessary but we recommend you make them during peak season (May-September) and public holidays. REX200 trains are not listed in the Eurail timetable. You can find a train schedule on the ÖBB website.
On the Eurail timetable Railjet trains are shown as "RJ", ICE trains appears as "ICE" and EuroCity as "EC". InterCity buses do appear in the timetable, but without an abbreviation. Reservations for these trains are optional but we recommend you make them during peak season (May-September) and public holidays.
ÖBB Nightjet trains appear on the Eurail timetable as "EN", same as EuroNight trains. For D-trains, only a trains number is listed. You're required to book sleeping accommodation in advance.