>>2660010OP here. I have a DR350, probably the best motorcycle ever produced. I ride singletrack with it, but can hop on a highway, not an interstate with it and cruise. The street legal DRZ400’s are too heavy and clumsy for singletrack. For woodsy singletrack, a smaller displacement dirt bike is better. You want the lightness for maneuvering, for desert you want a larger displacement.
Anything Yamaha or Honda would be awesome. They run forever and hold their resale value. My neighbor ordered a chinesium one from Amazon that seemed to make nice power and was light, but he’s always fixing something on it. I would look at a xr250 or a xt250 as a starting point.