In a way you'e both right but imo slightly missing the point re: what we need.
There is alot of talk about what we miss in terms of positions and mentions of whether it is Jorginho we need, or SMS or Ozil.. All linked to confusion on what we want Pogba to become and tactical confusion of how we want our midfield to set up.
My concern is more about the current composition of the midfield in terms of dynamism and coverage of the pitch.. and lack of control of possession against better sides or being able to wrestle back control of a game when it is drifting away from us in terms of momentum. Our big flaw is we have two really tall guys in there both of whom who don't really move around with quick fleeted dynamism and take a while to get those long legs going. Further more they're both not that elusive in possession, not really fast paced quick pass and go midfielders and are quite static in the way they move across the pitch preferring to get it to feet and holding off opposition using their physiclity and then making the pass. It is too slow for the modern game.
Our third midfielder will need to bring that dynamism and counterbalance the weaknesses that Pogba Matic have. Ozil won't really bring that dynamism, SMS is another tall, lanky player which I fear will exacerbate the current issue albeit he is class. Jorginho might be a good fit but we would still lack a more fast paced playmaker in final third.
Classic Jose midfield had more energetic diminutive defensive and attack minded midfielders and wasn't as height focused. Which allowed them to be robust defensively but also have lots of legs and dynamism in possession. Guys like Makalele, Essien, Cambiasso, Deco, Sneijder were mainstays of a Jose midfield and therefore I don't understand his current over obsession with physicality as you dont need talk players in such a dynamic part of the pitch.
I understand what you're trying to imply, but Matic and Pogba although not as fast, are technically as good as, if not better than those guys you mentioned with the exception of perhaps, Sneijder and Deco. It's probably a coincidence that two of our midfield signings under Mourinho are tall physical midfielders, rather a case of Jose being obsessed with physicality.
We need - like you said - dynamic players, but what we need also have to counterbalance the position we need and that means we need a dynamic playmaker to complete the middle too. Matic-Pogba's presence at the other side of the fulcrum means it has to be an advanced player in the Sneidjer, Deco, Oscar mould - precisely why I argued position-wise in the first post.
Adding a deep-lying playmaker and putting Pogba in an advanced role would make the midfield even more static as Pogba lacks the nimbleness to constantly evade tight spaces in an advanced position, meaning he will constantly drop deep, thereby creating a narrow midfield, restricting space and isolating the attack.
Kroos, Modric, De Bruyne are not faster than Pogba, it's just that they are quicker in mind and execution, and that is what the playmaker should bring.
Ozil although lacking defensively has those qualities. He's quite dynamic with the ball - although not good without it -, and his pace when moving with the ball is top notch. I'm open to signing a faster midfielder than Ozil though, but few could match his grace, precision and speed of passing.
Our inability to wrestle the ball back from the opposition in the big games also stem from the fact we use a low block, restricting space rather than pressing head-on to get back possession. Our forwards being Martial and Lukaku hardly help matters too. City have Sterling Sane Jesus, Liverpool have Firmino, Salah, Mane. Their midfielders are not flat-out faster than ours, it's just that their attackers are far more active out of possession. We look more dynamic with Lingard in the team for example.
Like I said before, I was arguing position-wise in my first post. Pogba, Matic, Lukaku and Martial are already here, there's nothing else we could do about that right now other than filling the holed positions with dynamic players. I'm open to signing any quality midfielder provided they play in an advanced role, not a deep one.