1. "Salzbur 7:02 RJ49" - that means even in Austria I am 'binded' to the morning Railjet? I've never seen it before for connections abroad... It's a first time I see it !! (nothing like that on the return ticket)
Well, apparently the problem pope-up because for DB website Salzburg is a DB station, thus in a situation like yours system simply interpreted Salzburg as DB and "assigned" particular train. At least it seems like an explanation.
Anyway, from my knowledge nothing really changed in terms of "zugbindung" and it's still about DB (+ gr. point) only.
Btw, a bit similar problem was already discussed in one of the ice-treff topics
here, so maybe it would be helpful to read through that as well (if my German doesn't deceit me, then colleagues ended up with the same opinion that any train can be used for Austrian part)
2. If for some reasons I am not binded in Austria, can I use any of the EN trains to arrive in Budapest earlier?
Not an OeBB conductor, but don't see why you can't
I don't see reservation obligation for both EN trains... (at least not in Austria and Hungary).
No, it's not required
It's only the one at 2am which is globally priced.
Well, de-facto "Wiener Walzer" is priced globalpreis in terms of SBB-OeBB/MAV, while "Imre Kalman" not listed just as globapreis, it's a "mix" with fares given both as "Aufpreiszug MAV - DB" and "Globalpreis Erwachsene"