Without being able to actually inspect the car it is really hard to say what is going on. The loss of accel & revving sounds more likely related to burned trans fluid rather than the alternator. The alternator may be coincidental? What warning lights did you get on your dash when this happened?
My only guess on the transmission would be that maybe the shop overfilled the trans. The overfilling whipped the fluid into foam, the foam failed to lubricate & cool sufficiently, the fluid overheated & burned, and your trans went south (hence the loss of accel & engine revving). The bit of smoke/steam you saw may have been trans fluid that had been forced out of the dipstick - thus the report of trans fluid under the hood & the smoke. If the shop hadn’t changed it at all it might be brownish. The smelling burned part really only comes from overheating.
So its all hard to say - at the very least I’d talk to the actual person at the dealership who inspected the car and try to get their best explanation as to what happened.