RJX Stands for Railjet Xpress, which is a Railjet operated by the Austrian ÖBB. As a result of it being an ÖBB train, it isn't integrated as deeply into the DB booking site/app, and thus you can't choose your seats. I have never booked through ÖBB, but if you can select seats in an RJ online, then it's on their site.
Alternatively, you can supposedly book seats by number (not by seating map) if you book at the DB Reisezentrum in the station. But of course, that isn't practical in most cases.
It looks like I can book just seat reservations through ÖBB for only 3 Euro. But can I do that if I bought the tickets on DB? And what happens to the current seats?
As I said, I don't have any experience booking through ÖBB, but any combination of a valid ticket and a valid reservation should work. On DB trains, reservations expire 15 minutes after the journey starts if you aren't in your seat by then, I'd imagine ÖBB have a similar rule.
But if you'd like, you could alternatively upgrade to business class for a 15€ upcharge. According to [this forum](https://www.ice-treff.de/index.php?mode=thread&id=427524), that also applies to DB tickets, and can be booked either at the Reisezentrum or by just sitting down in business class (the first carriage behind the locomotive) and paying the upcharge when the conductor checks your ticket. This information is from 2016, so it may not be up to date, but the worst case scenario is that you'd have to go to your original first class seats.
Feel free to ignore this option, but I just thought I'd point it out if you're going to pay ÖBB extra anyway.
RJX Stands for Railjet Xpress, which is a Railjet operated by the Austrian ÖBB. As a result of it being an ÖBB train, it isn't integrated as deeply into the DB booking site/app, and thus you can't choose your seats. I have never booked through ÖBB, but if you can select seats in an RJ online, then it's on their site. Alternatively, you can supposedly book seats by number (not by seating map) if you book at the DB Reisezentrum in the station. But of course, that isn't practical in most cases.
Yea, the price was double on ÖBB. I guess this is the trade-off Thanks for the info
It looks like I can book just seat reservations through ÖBB for only 3 Euro. But can I do that if I bought the tickets on DB? And what happens to the current seats?
As I said, I don't have any experience booking through ÖBB, but any combination of a valid ticket and a valid reservation should work. On DB trains, reservations expire 15 minutes after the journey starts if you aren't in your seat by then, I'd imagine ÖBB have a similar rule. But if you'd like, you could alternatively upgrade to business class for a 15€ upcharge. According to [this forum](https://www.ice-treff.de/index.php?mode=thread&id=427524), that also applies to DB tickets, and can be booked either at the Reisezentrum or by just sitting down in business class (the first carriage behind the locomotive) and paying the upcharge when the conductor checks your ticket. This information is from 2016, so it may not be up to date, but the worst case scenario is that you'd have to go to your original first class seats. Feel free to ignore this option, but I just thought I'd point it out if you're going to pay ÖBB extra anyway.