My heating works just fine. Years of neglect is the usual problem...
I regularly off road - proper stuff too, not just green lane.
The majority of it is spent in low 2nd, at tickover/low revs. Only use the clutch when stopping tbh. Mate with an auto is forever mucking about between various gearings off road and it's hopeless imo, although do see their advantages.
For the casual and occasional user there's probably not a lot of difference tbh, apart from steep descents - can't get decent engine braking with an auto and you'll sit on the brakes downhill. This, combined with the filth of offroading means your pads won't last long at all.