NW, what you say is only for serious mountain biking, and you may have to walk, is what I face when the small section of an unpaved road is full of water after a rain, on my commute home on my hybrid. There's usually space somewhere on the side or in the middle to ride, but I've had to walk, if I have forgot it may be wet. I only ride this way home if it's between 5 and 6, to avoid turning left from a busy road onto my street. I'd kill to see a dirt/gravel road like your last picture. Most of the ones around here are just full of rocks and gravel, and I've done them on my road bike, because DH did not realize it when he planned a route. There was a serious stretch of this on my 60th birthday ride, a few years ago. There's quite a few dirt roads with homes on them in one of the towns near here.