First of all, I have the Retrospective 10, not the 7 - sorry, I didn't remember right. The Macbook Air 13 inch does not fit in there (see pictures below). The 10 doesn't have a dedicated Laptop compartment, but it does have a rear pocket with a zipper that would hold a tablet nicely. Putting it in upright is probably not an option I guess.
According to the ThinkTank website the 7 is a little wider, but maybe not wide enough. The website says 11.8 inches for the laptop compartment, the larger MB Air is 12.8 inches wide, I came back late, otherwise I would have stopped at the local camera store to see if I could squeeze it in, but I would'n count on it. I might be able to try next week (The store is not far away).
I personally went for the UrbanDisguise v60 for occasions when I want to carry camera gear and laptop - It even hold the MB Pro 13-inch and the MB Air 13-inch at the same time in the laptop compartment. But for me that is rare, mostly when I travel by plane.
EDIT: The UrbanDisguise does fit under an Airplane seat.
When I'm out shooting, I don't need my laptop, and love the Retrospective 10 for that. It holds a 5D mark III with RRS L-bracket, with a 24-105mmL attached and lens hood, with 70-300mm L next to it with tripod collar and lens plate (hood reversed), and in the front pocket a Rokinon 14mm, filter pouch, and a 40mm pancake. The camera fits also with the 70-300mm L attached, and the 24-105 next to it.
The Retrospective 7 is a little wider, but has less height, and is less deep. I probably could still fit all of the above in the 7 (there is still some wiggle room in the 10), but it would be harder to get things in and out.
Not sure if that helps you at all with the decision making - if the laptop is a must-have, I can try the Retrospective 7 and the 20 when I'm in the store next week.