My advice - get the air bed. We don't ever turtle, but we do occasionally need a third a bed, and the jackknife couch doesn't really get it done.
One 5'9" person might fit on the dinette, but 2 adults would be a stretch. As for using it with the LR slide in, it would be difficult to get in and out of the bed. The air jackknife sofa has enough room to open with the slide in the closed position. Assume the air bed would - but not sure. However, that is a flush-floor slideout so the floor of the slideout comes up onto the floor of the camper. Not sure it would be a good idea to be using the bed with the slideout closed.
I would think if you wanted to turtle, you would still want both slideouts out. And we don't ever turtle. The front bunk will clear the tailgate of the truck, so even on an overnight stop in a monsoon, we put the bed out. With the attached canvas, its about 10 seconds of outside time to put it down. Even if we have to fold it up wet, its no big deal as long as we open it up when we get where we are going. If you spend the night the night in a Walmart or at a rest stop, this might not work, but we always find a cg with a pull through site for overnight stops so we have both beds and both slides open. If you stay hooked up you are only talking about an extra 10-15 minutes to get going the next day. And we're on vacation, so its nice to use the big kitchen space and all the other features that made us pick the IKSS to begin with.
But regardless - after 2 seasons of very happy use - our Roo had most of the options - power awning, power tongue jack, aluminum wheels, slide topper - all of which I didn't really care either way when we bought it. Now, I wouldn't change any of those, and the 2 things we didn't have on ours - air bed and night shades - would be 2 things I would definitely want if I had the choice.
Enjoy your new Roo!
2005 F-150 FX4
2013 Rockwood Roo 23 IKSS