First of all I would have really liked to see Guardiola managing an average team as well to see his quality better. Because he started his career with Barcelona B team. And the teams they have managed after that are only Barcelona, Bayern Munich and Manchester City. He has been really successful with these teams maybe. But I also agree that even an average manager would become successful with this kind of teams. Maybe he wouldn't be as much as Guardiola but the player quality would still help a lot.
However I must admit a fact that he literally built Manchester City according to his will after coming here. I think this is a very special time period of his career here because of that.
Can't guarantee with Pep Guardiola keep success as manager if manage teams with small budget, he was success with Barcelona, Bayern, Manchester City and third teams allocated unlimited fund for Pep Guardiola for signing potential players. No doubt with his smart strategies and right players transfer, but almost teams give him much money for active on window transfer and looks with how much million euro spent since last six years become Manchester City manager.
But achievement won Champion League with different teams made Pep Guardiola on the list name with experienced manager have won more than one team, Ancelotti won with tow teams between Milan and Real Madrid, the same with Jose Mourinho success won Champion League with Porto and Inter Milan.