Yes chess openings matters allways.
In the start you might have to learn moves that stops schoolars mate or early queen attacks. Now im currently trying to learn how to play vs various opening gambits. I have been deadlost many times because i made the wrong move vs some opening trick or tactic. So if i loose a game in the opening i try to go back and study that game to see what i did wrong and what I should have done.
Again....Depends. If the players are both beginner, or low rated. The odds are that one of them has just memorized moves with no understanding as to the "why" behind the moves. So if player 2 goes out of book and doesn't even know it, then player 1 will just play a move they memorized with no understanding of the position.