I am sure that you will get many answers on these questions. But this might help.
There are a couple of things about your observations.
It has been the norm for over a century now that the accepted hackling on 'North Country Flies (spiders are really those tied by Stewart and over time all sparse hackled flies have been grouped erroneously as 'spiders' so I am going tp refer to them as 'North Country Flies from which Clyde Style flies were developed) was no more than 2 and half turns. This light hackling was intentional in the design of them over 200 hundred years ago. If you are ever fortunate to see some of those flies (I even have some) you are likely to find that the hackle turns vary between flies and even within patterns. But 2-3 turns is all that is needed.
A heavier dressed North Country Fly does work, and IN have even experimented to see if there was any dis-advantage or advantage and experience seems to suggest that a light dressed fly works better IF FISHED CORRECTLY.
Now when you look a American dress 'soft hackles' they are dressed heavier and they are not North Country Flies or spiders as you call them. Generally American Soft Hackle are over hackled when compared to traditional North Country Flies. That is not to say they are wrong, they have been tied differently.
Who ever told you that hackles get twisted around the hook shank must either have a incorrectly tied fly or they are looking at it when it is extracted from the water at which time it is likely to look like a nymph. That is normal. What happens as you fish them is somewhat different. For example look at this:

Again, it is how you fish the flies that imparts action into the flies and moves the hackles.
Jim Wynn was a great River Keeper on the Wharfe and he was incredibly innovative especially as he had access to more modes materials. A bit of flash does work, especially on grayling - for example look at the "The Priest"
which has a silver mylar body.
I can tell you from experience that a traditional North Country Fly will catch as many fish as any other fly and fished in certain ways will out fish all of them. These old traditional flies are killers. They have just gone out of vogue.
By all means experiment and work out what you think.