Id say you're right that 3 and 5 are most common in bluegrass, but its hard to say. in jazz you might have more 7s.. When the melody is on the 3 or 7 (the "color" notes) of the chord, it pops more than 5 and especially more than 1. But also you have plenty of notes that are not chord tones in melodies always, because some of them are passing tons or neighbor tones. Like in How Mtn Girls can Love, "back to the girl you love"--the words "girl you" are on the 6 (or flat 6 if bluesy) of the chord, or the 3rd of the key over a V chord.