I've used the Gore Bikewear 3/4s which are made from Windstopper - they're nice, but expensive and too warm for me on a bike, plus Peak grit trashed the seat surprisingly fast. I suspect they'd actually make nice walking legwear, but maybe a little on the warm side above calf level and a little on the cold side below it.
That said, I reckon a non-membrane 3/4 would be good. I get on really well with the Haglöfs Lizard soft shell short - fearsome price though.
The fabric on the Rab Hueco stuff is 96% Nylon, 4% Spandex, so it will have some stretch. For comparison, the Sawtooth jacket, which is a pretty typical, double weave soft shell uses 90/10 proportions. I'd guess the Hueco will have a fair bit less stretch, but that should be about right for legwear maybe. I've not used them though, so it's a bit of an educated guess.