First off, hackle proportion is VERY subjective with the oft mentioned 1-1/2 to 2 times the hook gape needed IF you want a certain look or to keep the hook completely off the water.
That being said, I don't give a rats arse because I fish stuff with the hackle trimmed flush on the bottom and the fish don't care.
For the record, I tie parachutes with oversized hackle at least a size or so larger than usual because I find with it, they land upright more often and float better, especially in broken water.
I tie my Elk Wing Caddis (EWC) with palmered hackle and I like it just BARELY longer than the hook gap. Why, I don't know, I just do.
I also tie many single feather (versus Marinaro 2 feather versions) Thorax dry flies with hackle of a similar length to my EWC.
Most of my emerger patterns don't use any hackle, and with midges I take what I can get. 😉
FWIW - Most hackle gauges are at 1-1/2 time the hook gape so if I am using my preferred Whiting 100 Packs for dry flies, I use a size or two larger for parachutes and a size smaller for other dry flies. If I size my own hackle from necks or saddles for parachutes or other dry flies, I size them accordingly.
In regards to leader twisting, over sized DOUBLE wings, widely splayed double wings, double wings or too long single wing posts give me twisting issues more than anything. For that reason IF I tie any fly that calls for split wings that ISN'T going in a shadow box...
I use a single correctly sized poly wing post instead.
BTW - IF you are experiencing bad twisting and a heavier or stiffer tippet doesn't help and you don't want to butcher your fly, SLOW DOWN your line speed dramatically, which helps a LOT.