Are you saying that fingerstyle guitar relies on notes to sound that have not been struck, picked, plucked, or otherwise molested by the human hand? Are you sure about that, because that is a new one on me--and I have been playing these things for mearly forty years--If the music tells you to play C and G, it doesn't want to hear from any E note, and there is not much point in fingering it--In fact, it is a good practice to finger only the notes that you need and not keep your fingers locked in a full chord position when you are using only a couple of the notes--the D note shouldn't sound unless you pluck it--you can deaden it so that it doesn't ring, which is sometimes necessary on an electric or amplified guitar--but that is something else--

Classical harmony allows that to have a chord, you must have a triad, which is to say, some rendition of the first, the third, and the fifth. 20th century harmony allows that you can honk, squeexe or mash any three notes, and assign a pitch and note name to them in whatever way you have contrived, be it drunk or sober--you have to make up your own names for them though, as the chord names from classical harmony don't fit--