I shoot 2-under and have for the past 4 years.
It makes sense to me ---- though I could be wrong ---- that 2-under, if you have sufficient finger strength, is better than 3-under because the shooter has less physical contact with the string.
Look at the mechanical releases used by compound shooters. All of them feature very little string contact. If more string contact led to better accuracy, wouldn't those mechanical releases be designed differently?
Mark