The idea is that we have a bunch of youngsters who have different skills and different flaws.
Gavi is physical and pretty fast, able to contribute in both defense and attack, but so far lacks vision for key passes.
Pedri is the most all around matured of all, but lacks speed and this is why he doesn't do very well in attack. Normally Gavi and Pedri are the most alike, with speed and creativity reversed.
Puig takes the most risk, is fast, best dribbler of all, has the best eye for pass but is agitated and inconsistent. Also can suffer physically because he is short and skinny so this would make him the poorest defender if you don't press high.
Nico is strong, fairly skillful, but looks slow and also makes the most technical errors out of all four.
So, we need a manager that will integrate their skills and know how to mask their flaws by coming up with a proper plan.
All 4 should play. Pedri the most minutes because he has the most experience by far.