Here's a great link...
Werner
There's some good pictures there. I'm a low angle paddler myself. If i'm really trying to go fast, my style goes to high angle. But 90% of the time, I'm cruising and enjoying the low angle.
As for being easier on the shoulders, I want to say low angle is probably a little easier. As I sit here (and look like an idiot) and pretend to paddle my invisible kayak, I feel like my shoulders don't rotate as much with the low angle.
If you have shoulder issues, grab a mirage drive kayak. Just my opinion.