Hi,
I could do that on 23's If I wanted (just agreeing with you), But anyone who
rides on 23's would not struggle they are just a bit harder on the rear
The downside is if you don't slow down the risk is loss of control due to bumping around some and some loose stuff, more so going down, any off road is the same.
Going down would be a different story due to increased speed but still easy for anyone who has ridden a bike at least once in their childhood.
But if you are careful can do anything on any tyre and bike.
Its mostly very fast for off road, any bits that exist today where anyone apart from the extreme riders will have to dismount are very short and take minutes seconds even not a long slog through mud.
Its a nice fast easy ride, the detour around burrator is pleasant and should take yopu no more than 30 minuts or so added to the trip, if you don't stop for ice cream
But from burrator you will spy several tracks which lead up to princetown via several routes which if you try you will be lost in heaven for some days
The main route to princetown over the moors via tracks is a bit rough and you would really need tyres approaching 2 inches for that.
Dartmoor has many track that take you over moorland where you will be all alone, walkers will be rare and cyclist even rarer, but easy to follow with a map and even camp too. That's for another day but real camping no houses no people only the animals you would expect to see on moorland................the quite is deafening too
You can do most of this stuff on a tourer 700 tyres at 35mm will suit minimum for this stuff, preferably with some tread.
There is no cycle route except off road, yelverton to princetown except purpose cycle track including old railway its a bit rough now, used to be better and its only weather that has made it that way today, when tracks go in and get used water runs down and washes away the loose and silt so rocks are exposed, but all ridable at careful pace with some very fast sections at parts.
Good luck.