I was recently mulling over how much we used to camp vs how little we camp now, and realized that the setup which was most favourable for a quick camping session was in fact the small off-road railer with a quick-setup RTT on it. It was a great setup, and at times I do miss it.
However, when it comes to off-road adventures with a trailer, I'd caution everyone considering the option to think about the kind of off-road adventures THEY do, and their specific terrain. We're in the pacific north-west, with a ton of forests, steep mountains, and tight, overgrown trails. I've come to the conclusion that it largely doesn't matter whether I have a tiny off-road unit, or a 20ft, 4500lb travel trailer behind me. The limiting factor is always the same: ability to turn around.
In other parts of the world you may have more open terrain where finding a place to turn around is a trivial task, and so other limitations will come in play.
I'm glad you touched on this. The ability to navigate tight trails and turn around is key in my mind for an off-road trailer, which is why I lean toward smaller and lighter. Even in the southwest where it seems like wide open expanses, we're often in trails that exist in canyons, washes, rocks or trees meant for jeeps. Can only seek so much adventure if we can't turn around. I understand this isn't everyone's idea of adventure, and some may only go as far as federal or state parks. Which I do too, but I have a larger trailer for those trips so I don't have to walk the middle as much. Then there's tons of middling destinations between those.
Criteria for my off-road trailer is having a track definitely no wider than my tow vehicle, and preferably narrower. Tongue that allows up to a 90* jackknife turn. We've had to decouple friends trailers many times in a pinch and manually turn it around separate from the tow vehicle, which means ideally tongue weight <300-400 lbs.