From what I read, his new racquet was supposed to give him more control
It's what he had in Roland-Garros, and the new strings from this year were also supposed to improve that specific point.
My bad impression was rather the opposite
, that his shots were less explosive
That's what I had heard should be the effect of the new strings especially : more control but less explosivity
As for his volleys, well imo he has never been good at volley, then I didn't see a real change