I've slept in my '00 and '04 a couple times. With the seats folded flat (rear seat bottom flipped forward, pretty big help for getting out of the rear side doors), cars101 says there's 5'8" of cargo length. When my wife and I slept back there on our UP trip, I could not stretch out (not a big deal, as I'm a side sleeper anyway). Without folding the seat completely flat, you probably get about , but the front is elevated. This makes getting out those side doors very difficult, and would not really be possible with another person in the car. But, with a modification to the rear gate to open it from the inside, that would be sweet.
Here was the latter setup (with truckbedz air mattress):
2018-10-15_02-49-50 by Numbchux, on Flickr
The CRV has a 10" shorter overall length (according to wikipedia)...no hopeful for interior space. Forester is similar.
The BE/BH Outbacks come with 3 different AWD systems. The most common, MPT AWD on the 4EAT transmissions is very FWD biased, and can send power to the rear as needed (to a point). This is controlled by the TCU, and pretty good. It can also be easily modded to "lock" (still not 100%, but better) with a little wiring and a switch.
The manual transmissions are simple, 50/50 mechanical differential with a viscous LSD. The LSD tends to get tired over the years, but there's a company in Europe that can rebuild them, and even make them stronger.
The VDC trim cars have VTD AWD, which is a 50/50 mechanical AWD AND electronically controlled clutches. Downside is these cars come with stability control, which limits the fun a bit. But the ABS isn't ridiculously intrusive.
The cold weather package (heated seats, mirrors, windshield. An option on the early ones and standard on the later ones) on the non-VDC models came with a rear viscous LSD as well. These LSDs aren't very strong, but every little bit helps. Unless you plan to use the torq masters locker, in which case you'll need an open diff.
I have a '00 5MT with cold weather, and a '04 VDC. I've had them both off the beaten path, and they do fantastically. As always, though, a torque converter gives you so much more control at slow speed (we usually take the '04). I don't even want to talk about having a clutch offroad unless you have at LEAST 100:1 crawl ratio, preferrably more like 200:1 (best combination using Subaru parts is about 25:1).
The CRVs have an AWD very similar to the Subaru MPT system (FWD biased), but just uses a viscous coupler to send power to the rear. The Honda Element rear diff is a direct swap, and has a stronger coupler.