You still don't get the point, who's talking about better performance here, you can still perform better and lose the match. I'm talking about Barca's high line defence which keeps the opposition offside when they attack to score. Barca players are not relaxed, it's just that they didn't penetrate the the defence of small teams than they do for big teams, besides most big teams don't like to defend, they attack which opens up loopholes to exploit by Barcelona attackers while their defence keeps the high line just incase of any counter attack from the opponent.
You understand this football thing, I observed this very well in the first El clasico they played with Real Madrid. They Mbape looks like he is an amateur because he saw many opportunities to score, he even attempted them but he was found to have offside very well but some teams understand their ways. Right after the match, they lose many matches with that behavior as some team studied their playing tricks, they lose even without scoring goals.
Barcelona improves as times goes on and as it is right now, I have confidence in them than even Atletico Madrid. The two teams above them might be grinding now but the fact that they were able to take super cup from Real Madrid and score many goals against them, here is not a rocket science, they will win this Laliga surely except if there is a reported case of injuries to any of their prominent players, it's not likely but never say never.