Ray has given a very good summary. In recent years the festival has become more oriented toward Bluegrass since the big old time festival is the week before, at Clifftop, and few of us can take two weeks off and do both! (Last time I was at Galax was 2001)
1) In general, if you have a camping pass, your neighbors will be the vehicles immediately before and after you in line.
2) Despite what I said above, there are enough good old time musicians there to make going VERY worthwhile, and they're all very friendly and approachable.
3) As Ray has said, bring rain gear as well as hot weather gear. Felts Park is at the bottom of a saucer, ad the August heat can bake you, even at 2200 feet above sea level. Then it gets cold at night, with a heavy dew. . . just the thing instruments need to stay in tune (joke here)which may be part of the reason for some of the things I have heard from the stage