Martin is right. For Bluegrass and Old Timey you're going to play a lot of open, first postion chords - because they "ring" through.

And, if you need to go into Bill Monroe land - B or Bb - you just capo up and still play out of a G postion.

I've played with some old time fiddlers who got real upset if you tried to play a barred G or A or a closed C7 form moved up the neck.
One stopped in the middle of a tune and said "play the damned right chords!!"

Of course if you're playing with Western Swing fiddlers they want just the opposite.