That right side again with Pedro and alves.....
To be honest, that looks to be Lucho's tactics. Pedro playing more centrally to draw one centerback from Messi, Neymar playing out to the left to bring most play down the left side, Alves wide open on the right (to cross, unfortunately, but Lucho seems satisfied with playing that roulette, as long as it turns up a goal eventually).
As far as Pedro vs Munir/Sandro/etc, people forget that he is (and always has been) the most conservative of the forwards. While Munir/Sandro may be more offensively aggressive (and possibly productive), they have yet to be proven for ball retention and recovery. In the last game alone, I remember Pedro winning loose balls multiple times, protecting it and getting it safely to a teammate. Lucho may feel the tradeoff is too great, that there is plenty of scoring potential already on the field, and he wants that conservative ability in the final third to make sure the team doesn't end up on its heels defending counters too often during a game.