I made a quick video showing how the 1025r turns in the different drive modes - on gravel.
I think it turns quite well in 4x4 but 2WD certainly can turn sharper.
The difference between 4x4, 4x4 + diff lock and 2WD + diff lock is not great but noticeable.
In order from best to worst turn radius:
2WD 4WD 4WD + diff lock
2WD + diff lock
Especially in 4x4 + diff lock the weight on the front wheels will make a big difference in how it turns. From terrible - like when going up a steep hill with a light front end, to very good - when the front end is heavily loaded.