LH Position and String Muting

Like everyone else said it's just practice.

You see people banging away on the strings yes...but you get to a point where it becomes muscle memory to where your body is in relation to the guitar and strings. So short answer is YES, you get to a point where you don't need to mute.

You'll hit the errant note once in a while, nobody...and I mean nobody, is perfect all the time.

The less fingers you need to use to make the chord comfortably the better. Wrapping your thumb around the top when you don't have to can create a strain in the wrist depending on your posture.

Keep at it!