Well, I guess that's why they say, different strokes for different folks. The paddle I use the most, has the degrees marked on the shaft and I know from lots of experience where to adjust it for varying conditions. Because of the excellent cam, there is no doubt about the blade position--without having to look before insertion.
I have found that about 40 degrees of feather is fine for moderate head winds, but when the wind really picks up, I will go for 90. That allows for a lot less wrist flexing for the control hand in all but the stronger winds. The infinite adjustability also allows for a slight feather that seems to work well for me when for all intents, I'm non-feathered.
Anyway, I've learned from my own experience and from some very old time paddlers that whatever works best for the individual is often what is best. That's not to say that I'm close minded about the whole thing. Heck, I'll try almost anything--even a stick (GP).
My thought about paddle length is that you can make anything work, but as you change boats, it is nice to be able to switch to a shorter, or longer shaft, and the width of the boat is not the only feature that might prompt a length change. All of my boats sit a little different with respect to position above the water. I like to be able to completely submerge the blade without changing the amount of twist and lean (if any) that I have grown accustomed to. My favorite paddle works equally well in both sea kayaks, but when I switch to one of the rec boats I use a longer paddle that has the same kind of blades.
The bottom line for me is that if I could have but one paddle, I think it would have to be adjustable for length and infinitely adjustable for feather. There are such animals out there, but so far, I haven't gone that way.