Hi there,

This is a good question. The basic explanation is that, there's no hard rule for how to place your fingers to make a chord. General rule of thumb is to do what's comfortable for you, but make sure your fingers aren't so wildly off that it will hamper your progression later on.

I think it's perfectly fine to use your 2nd and 3rd finger to play an Em. I switch between using my 1st and 2nd finger on Em, and using my 2nd and 3rd, depending on the chord progression. Sometimes I even find myself using the 3rd and 4th finger (pinky) after sliding down from a F or G barre chord.

Do whatever works for you, as long as it's comfortable and easy enough for you to switch to the next chord.

I hope that helps!

Best,

Billy