Kante is the textbook definition of a defensive midfielder. There's a hispter-ish trend to say he's good with the ball, but he's Championship standard at best. You compare him to KDB as he's the like for like here which makes total sense, but barring the energy levels and willingness, Ederson would be a better comparison to KDB than Kanté if we were just looking at ability (slight exaggeration, Eddie's not that bad :p).
Normally, that's ok. He's a ridiculously brilliant midfield destroyer. And this is during an era of football where that role is harder than ever. Play him in that role and you will always benefit.
You could play him alongside Jorginho, but that would kind of compromise the system. You lose the scope for one to defend and the other to play as universally on the pitch. A midfield two a la Scholes and Keane just wouldn't cut it these days. You could move Jorginho forward and adjust the system, but as we're seeing already Jorginho in the DM role is not changing (which if you know Sarri makes sense).
And it's different for example, to if he signed for us and working him with Fernandinho. Because for 1, Pep's less rigid with his formations, so two DMs isn't beyond the realms of possibility. And 2, whilst Fernandinho is no KDB he's still got just enough quality to give the forward CM role a good go if he had to play ahead of him.
When we played Chelsea at Stamford Bridge, IIRC they had Kanté on one side and Bakayoko on the other. Kanté made a really decent showing defending his side of the pitch, but they not only lost his defending on the other side, but they were undone every single time he had possession. He ONLY really works when you have in in a role where he can do what he does best; be a defensive nightmare all over the pitch. That's where he's world class.
It may work out though. Class tends to find a way to show itself in the end. It'll be interesting though because Kanté and Jorginho are arguably the two most specialist midfielders in the world, and their styles on paper clash massively. I'll assume that when Kovacic and Hazard are available, and everyone's up to speed, they'll be able to cover up this issue for the most part.