I don't think we are a particularly good pressing side. It's as though we have to put our mind to it rather than it be automatic part of our game.
So if our front 3 are 'closing' rather than 'hounding' that's enough of a time difference for (good) opponents to find the balls between the lines or onto their CMs where they are generally outnumbering us 3 to 2, hence the problem. It puts an enormous amount of work onto PEH and Bentancur, which tbf they admirably cope with. But against the very best it might crack.
Not forgetting that against the very best we are quite comfortable sitting in that low block 541 and dealing lethal blows on the counter.(As an alternative way of dealing with it)
The reason it's a tricky call is there are many teams (in the PL), and games, where a team can surprise you with their quality. Saints is a good example, they really have out maneuvered us in games previously , yet the opening home game we controlled, looked dominant, physical and effectively steamrolled them.
It's a headscratcher for Conte, as it was for previous managers, it's almost a consistency problem that they have difficulty explaining or understanding.
We won't be a great pressing team with Kane and Son in the team imo. We can do it for shorter spells.
We accept getting pushed back a bit more for periods. We accept being "outnumbered in midfield", because we know the threat of Kane, Son, Kulusevski and our wing backs should still make us lethal on the break. And we know we're capable of being solid at the back playing like that.
When/if we're unable to launch counter attacks (or play out through pressure) that becomes a real issue. Opponents dominate, will create some chances at least and we create very little. Long sustained periods of defending and little else.
We really only need to launch a handful of good breaks during a half of football to go from not a good look to looking rather good.
To me the solution is better ball players deep. Defenders, wing backs or deep midfielders. Launching good breaks becomes increasingly more difficult for every player in our team that's not up the job of playing through pressure effectively.
A Modric/Dembele/Carrick type player would obviously help, but only so much. By having weak spots in that regard it makes the job so much easier for the opponents that I don't think even an excellent ball player in midfield makes enough of a difference.
The teams that are very good at that become good by individuals being very good, sure, but just as much by having no weak spots.
Imo Sanchez and Royal are weak spots in this (rather specific) regard. Reguilon too. Jury still out on Sessegnon. To overcome the headscratching inconsistency you talk of we need better that that.
Not that we need better to keep doing well, to win games, to have great performances. But to minimise those really frustrating periods like against Chelsea, the Wolverhampton first half, we need better.