Woo hoo! Finally something that I know about. I've flown the combis many times. It all depends on how much cargo AS
decides to carry. Since it's in summer I would assume that the plane will be mostly passengers.
Right now, according to their seat maps for your dates and flights, it looks like rows 1-7 will be missing for the cargo. Most likely, they won't remove any more rows, but check back closer to your flight.
As for seeing Denali (as the locals call it), you probably won't see it because the weather is almost always cloudy around the mountain all summer long. If you see it, it will be most likely on the early morning flight because that is when it's clearest. The unfortunate thing about Alaska is that in summer when the tourists come, Denali likes to hide. In winter on the other hand, it is visible quite often, from Fairbanks at least.
As to where to sit. I would recommend sitting closer to the rear of the plane, behind the wings to see anything. The flight path is east of Denali, so sit on the left heading north, right heading south. Also remember that the plane boards from the rear so you won't be using a jetway. Wear something that you don't mind getting wet in case of rain.
Semper ubi sub ubi.