The bench is strong as pointed out earlier, but also where he replaces is weird with the new systems in the team.
He can't replace Mendy anymore because we now use our LB to go wide, only Angelino is capable.
He doesn't play David or Kevin's role quite like them and is more defensive, so unless we play with a double pivot he cannot rotate in there.
The only other player to replace is Rodri as a single pivot, but Pep uses Gundogan there more (and he is really good at it).
He can played inverted LB, double pivot, or LCB in a back 3 from what I've seen. I think he plays (or makes the bench) if we use systems that use those more like 3-4-3.