I never traveled that route, but I frequently use buses for short and mid-range trips.
In case you don't know, this site sells tickets for most bus lines in Argentina
https://www.centraldepasajes.com.ar/
In there I see that the route you are interested in is served by Andesmar, and takes 10.5 hrs...$40 usd...The only service offered is "semicama", lingo for a reclining seat....it is probably just a single-deck bus. I would have preferred a "cama" service for a trip this long, which is again a seat but that can recline much further to almost horizontal.
The bus line itself, Andesmar, is good. I used them for other routes and I think they are fine, average for bus service in Argentina. I would expect a newish bus, hopefully with functioning ac. Beware that the schedules posted (in particular for your case the arrival time) are always subject to some delay, so don't plan on a tight transfer in Salta
Another story could be your fellow travelers. I don't know what is going on with people but seems that everybody loves to send/receive audio whatsapp messages all the time. Bring something for your ears.
good luck!
www.busbud.com
