Yeah, in a live league you and your opponent can get all your games out of the way at once, if you want to.
And if an owner goes missing, your games with him will just sim as they would in a regular league.
You're not required to play all your games live anyway. Most live leagues have a live game minimum in place (like 40 or 60 or 80 games) that you have to reach in order to qualify for the playoffs. There are usually a few owners in every league who, for whatever reason, don't reach the minimum.