Be sure to check out their forums - the owners there are always willing to answer questions and I've found that they are honest and objective when it comes to giving critical reviews of their trailers. Many are eager to show their trailers if you can find an owner nearby. And a handful are members here as well. But if your Dad is close to the factory, then I highly recommend driving over for a factory tour to see the trailers in person.
I think they're great, but then I'm biased as I have one in their production line at the moment.
As for the shells, they are laid up using layers of fiberglass matts, composite panels and aluminum reinforcing plates with chopped fiber between. They are...strong. FWIW, the owners use and abuse their trailers regularly. They're avid campers and hunters and they've built the trailers to handle bumpy gravel roads and harsh weather. It's a true four season trailer.
For overlanding and offroading - it's not a small trailer but that aside it adapts pretty well to softroad travel and backcountry camping. The smaller one is of course better suited for narrow forrest roads. Mine the larger model but is being lifted 4" above normal for better clearance, disc brakes, 640W solar, lithium batteries, isotherm fridge, composting toilet, on demand hot water, etc. For point to point overlanding, it's size is limiting; but as a base camp for making overnight excursions in the truck, I think it's about perfect.
For your dad, I wouldn't worry too much about the tires, and the trailer should go just about anywhere a Suburban will fit. You might consider swapping the axles to an overslung arrangement for a bit better clearance, and I highly recommend disk brakes. There's a push to get Oliver to make those standard or at least offer them as an official upgrade, though it's an easy upgrade to do yourself. If he wants to avoid using a generator, then swap out the batteries for some dragonfly/battle born lithiums and get them to install a port for a set of portable panels. They might also be able to add an extra 160W panel on the roof if he doesn't put any TV antennas up there.