Reply To: one or two eyes??
It’s all about eye dominance, those that have a strong eye dominance can usually shoot with both eyes open, but if one is ambidextrous they will find they may have a harder time focusing in the scope because the other eye will fight for dominant focus.
I will say this, you can train yourself to shoot with both eyes open, if you have a problem don’t get a patch instead get a blue or green plexiglass single eye shield that is medium dark tented. What this will do is force eye dominance to your shooting eye while at the same time allow your other to see. You can find these in target archery fairly easy
One factor with shooting with both eyes open is SAFETY, using a scope places you in a tunnel vision situation I.e if you are right eye shooter then things coming from your left will not be seen till they cross into your scope line.