I've only been in the call making business for about 5 months or so, so I haven't had time to work with many woods yet, but I do have purpleheart and hickory strikers and I have to say, I love both of these woods for strikers. At least for my pot design, I get a lot more rasp with a purpleheart striker and a slightly higher pitch than I do with a hickory striker. I love both because I can get raspy and aggressive with a purpleheart striker, and a little softer and clearer with a hickory striker, all while using the same pot call.
I wish I had more experience to answer some of your other questions, but I will say that wood grain affects sound quality as well. So if you had two woods of similar density, the grain of the wood can make a big difference on the sounds they produce.