Re: Nymphs v. Soft Hackles
I think all angles have been covered but I'll add my two cents anyway. I fish a LOT of soft hackles; through every part of the water column. In (moving) water that's two to four feet deep, I like to use a sink tip line......up and across, let it dead drift and then let it rise at the end of the drift. If I want to fish the bottom section of the water column, I may add a split shot or go to a tungsten bead soft hackle. Of course, if they really are nymphing on the bottom and, I have an idea as to what they're eating, I'm certainly not adverse to switching to an actual nymph.
In shallower water, or if the fish are feeding in the upper column, I'll use a floating line; I'll still dead drift but might give the soft hackle a little quiver towards the end of the drift. And, as Joni alluded to, it's no crime to squeeze the water out of the soft hackle, brush on a little Frogs Fannie, and let it drift right in the surface film like a 'dead' something or other! This is also a good time to try something small and dark (ie. black spider) and fish upstream to likely looking lies. Just think 'little terrestrials and bugs falling out of the trees'.
Since they're so 'impressionistic' you can just be close to what the fish are looking for and still get takers. I tie them in sizes from 10 (which I think are more or less streamers-not counting green drake emergers of course) down to 20's; tans, olives, orange, greys and black are good for starters although Auntie Em recommended some blues or purples and they're next on my tie list!
What ever you do, they're a versatile fly and a lot of fun to fish.