PEH is very tactically and physically astute, he just lacks a bit on the technical side. Which sometimes render him incapable of performing the action he wants to, which I think makes him slightly nervous on the ball when he hasn't decided what to do.
He's a good midfielder, but you cannot let him come under a lot of pressure. He needs outlets and options to minimize the possible pressure opposition can risk putting, which in a 3-4-3 should be provided by the other midfielder and both wingbacks. Conte also likes to have his outside CBs go up in midfield at times, which has most commonly been Davies the last season.
This is partly why the combo of Reguilon and Emerson was fucking disastrous, and when they don't position correctly, Davies also has to stay back. Meaning there is ONE (1!) option left: the other midfielder.
Now, imagine the ease this creates for a team adept at pressing. Just press the two midfielders and you're done.
Sessegnon and Doherty definitely alleviated this issue as a pairing, but it's not quite enough.
I imagine Perisic will help our midfield greatly on this issue.
Bissouma + Hojbjerg/Betancur will definitely be very annoying to face for opponents.