In fairness I'm assuming what are final incoming list will be the following:
Gundogan
Nolito
Zichencho
Rulli
Sane
Stones
Peres
I really don't see how we get Kroos if United gets Pogba. The basis for us getting Kroos disappears if Pogba goes to United. So like I said if they get Pogba, I think that gives then the edge, not only coz they get him but also because it more or less guarantees that we are not getting Kroos.
If my above list, which already at 7 seems alot, is where we stop, United's 4 were they to get Pogba gives them an acquisition edge in terms of proven quality.
That said, like I pointed out you still have to build a squad out of your pieces regardless of how talented your acquisitions are. So it doesn't guarantee anything in terms of trophies, but on paper it's hard to argue the most moat sort after midfielder in Italy, the most productive striker in France and the most productive midfielder in Germany does not equate a better haul.
In statistical numbers
Zlatan was the highest rated player in France, Pogba in Italy and Mhkt in Germany. It's hard to argue against any team that gets all 3.
Kroos was just an example, we've been linked to a fair amount of players otherwise.
You're making an assumption about how many players we will sign, which is OK, but that doesn't look at the full picture. Sure, if you weigh up Gundogan, Nolito, Sane, Stones and Zinchenko against Mkhitaryan, Zlatan, Pogba and Bailey, then on the face of it you would think United have the better signings and are thus in the better position. However, as I said before, we start in a position arguably better to begin with and simply weren't used effectively enough.
It's also easy to point out "Player X was the highest rated player in country X" but then, look at Otamendi, that doesn't necessarily hold water at all. Zlatan was the highest rated striker in one of the easiest leagues/teams in Europe to be a goal scorer. Mkhitaryan played on a squad leaps and bounds ahead of where United is right now. Pogba is Pogba.
The reality is we aren't done making signings and we already have an exceptionally strong squad teeming with talent. Even assuming we stop where you suggest we stop, a lineup with Aguero, Nolito, Sane, De Bruyne, Silva, Gundogan, Fernandinho, Stones, Kompany, Sagna, etc still looks hard to beat, particularly with Pep at the helm.