well the way i see it, the neck is a resonant structure and influences the string vibration heavily. the fret board shouldn't change the resonant frequency of thew neck significantly or at least i dont imagine that it does but will effect the transfer of energy into the neck. an oily or waxy fretboard might dampen the sound and change timbre while the neck wood can change timbre as well as add or cancel different overtones, neck mass would presumably come into play as well. the body is the biggest radiator of sound and is probably more heard unplugged than plugged in but that is not to say it is insignificant. as far as percentages go i have no idea, as long as the guitar isnt made from cheese im sure it will sound fine.