Keep in mind that with electrics, you are giving up realism. Your airplanes will no longer sound like airplanes, but more like hair dryers! Corn poppers?? Bah Humbug!
1. Sound generators can replace engine sound.
2. My Saito 50 was so quite I could only hear the prop noise, not the engine sound.
3. 2 strokes have a high pitched whine, nothing the the roar of a Rolls-Merlin.