The answers to your questions would fill several books, and I haven't the time at the moment! I'll just start off with a couple of listening recommendations.

Saw one of the very best last night, Ralph Blizard and his band, The New Southern Ramblers. Check out the sound samples at CDNow He's gone now, but I also highly recommend Lonnie Robertson

Here are a bunch of links to explore The very first link on the page is one of the best, but it has moved and can now be found at http://www.oldtimemusic.com/ You'll find enough there to keep you busy a while. The Old Time Fiddlers Hall of Fame would be a good place to start, I think.