I'm no expert but I find all this interesting.
I made my own paddles for years and they had no angle on the blade.. and I liked it.. I liked the way it didn't matter which way the blade faced.
I then used new C4 and realized there's something in this blade angle thing and I liked it better..I liked the extra reach..I like the way the blade released from the water.
I once saw a picture of Laird and noticed the extreme angle on his paddle.. It was a QuickBlade.
I've since tried them all.. The QuickBlade feels a but odd at about 14 deg.. It has even more reach than normal but the blade doesn't seem to start to work until the end of the stroke..Right where max power is.. I can see why Laird would like it.
The C4, Werner and Kialoa are about 12 deg and I think that feels just right.. (maybe that's because it's what I'm used to now).
Yesterday I saw pictures of the new JP paddles and they look only about 8 deg.. Almost straight.
I'm thinking thinking if you want heaps of power with a long stroke the more blade angle the better.
I think if you want to paddle with a faster cadence and shorter stroke a blade with less angle is better.
I think you still need some angle because it helps the paddle slip out of the water at the end of the stroke.. plus helps to stop lifting water at the end of the stroke..and also helps to lift the board with each stroke.
I know Dave Chun from Kialoa is working with Chuck Patterson on a new race paddle and it will be interesting to see what angle the blade is.
He did tell me that it will have a slight dihedral in the face but that's all I know.
I'm not sure if that helped any but that's my two cents worth..

DJ