I have taken our Forester (2010, with a 4EAT transmission) on the sand in the outer banks before (stayed in Hatteras village, took it out to the inlet). I got the permit from the national park service center at Pea Island.
No problems at all. I took the same precautions you should take with any vehicle on sand. Stick to the harder stuff where possible, have recovery equipment, etc. Any vehicle CAN get stuck in sand, but if you're used to sand driving, a Subaru should be fine. Light weight, when compared to trucks, helps a lot, and you float more easily. Airing down helps that further, of course. In those senses, a Subaru is actually superior to a truck on sand (though something like a Jeep Wrangler rules). The ultimate step is to get wider tires, preferably with an A/T tread pattern. That's where the Subie is limited, as it won't take real wide tires.
We've not yet had the OB down there, but don't think it'll be any different. Was a little concerned about the CVT, perhaps overheating or something, but reports on this forum have me less concerned about it now.
8.7" of clearance is very good for a car. It's more than many body on frame SUV's and equivalent to your average mid-size truck. Both axles are always engaged, though the Subaru varies the amount based on a million different variables (acceleration, turning, slope, etc). That's assuming no slip. The bias (meaning going straight down a level road at steady speed) is said to be 60 front/40 rear, but from my understanding it almost never is exactly 60/40. If slip is detected, it'll increase pressure on the mutli-plate clutch, i.e. bias more towards 50/50 front-rear torque split, as well as brake the slipping wheel to simulate an LSD. In older versions, like our Forester, manually putting it into 1st or 2nd gear would bias the torque split more towards 50/50 front-rear and make the car more "reluctant" to allow it to vary. I'm not sure whether that's still true in the new version, but the addition of X-mode should do the same thing, as well as make the simulated LSD wheel braking thing more sensitive.
That ABS enabled braking is where you have to be aware that Subaru AWD does not act like a 4x4. In non slip situations, you still got torque going to 4 wheels, which makes beginning to slip less likely (and this is why lesser AWD systems that default to FWD are inferior). But if you do get into trouble and start spinning tires, a 4x4 is just locked in, and a mechanical LSD transfers torque immediately. But in a Subaru, you may have torque to both axles, but left-right torque split is through open diffs. So if one wheel on both axles are slipping, they get all the power, and you don't move. That is, until the point where the system sees that you have a problem, applies the brakes to the spinning wheel, which throws torque to the other wheel, and you go. Under normal circumstances, perhaps there had to be a 20% difference in wheel speed between left and right wheels on the same axle before brakes would kick in. Otherwise it'd apply brakes during simple turning, which isn't good. Hence, if spinning, counterintuitively you should apply MORE throttle, and once the spin hits a high enough speed the system will respond appropriately. With X-mode on, it lowers that threshold so that it responds quicker, though none of us know by how much. But this is why you shouldn't leave X-mode on all the time, just like you shouldn't leave a 4x4 locked in all the time or you'll hop wheels and stress transfer cases and differentials when turning. As was said, I do believe X-mode shuts itself off, though, once vehicle speed hits a certain threshold, so it kind of protects itself.