No one mentioned
I don't think anyone mentioned shaft shape. That is the part of the paddle shaft where your hands rest on most new better paddles. They aren't oval shaped just for hand comfort like some people seem to think. It is so that your hand can recognize the blade indexing and you can keep your eyes trained elsewhere.
A long time ago, I really never fully understood why most Euro-paddles had this often radical feathering capability. On this one occasion, I was paddling into a wind that became increasingly strong and very gusty. I was paddling with zero feather and then when a couple of very strong gusts almost took the paddle out of my hands and nearly brought the boat to a halt, a light went on and I figured it all out.
Where I paddle most of the time, the wind is either blowing up, or down the river, so unless I'm just paddling across the river, at some point I'm paddling into the wind and it does make a big difference if you're trying to push the flat surface of the blade into the wind for hours.
I've played around with minor feathering and I've finally settled on zero for downwind, or no wind and 60 degrees for going upwind, but if the wind is very strong I might go to 80, or 90 degrees.
I have to thank one of the members here (Jack L) for educating me about not feathering with abeam winds. This happened quite awhile back when a similar thread came up. Since as I stated, where I paddle, the wind is seldom on my beam, I never thought much about it, but when it was brought up, that light came on again.