4-3-3 is not magical formula. 4-2-3-1 or 4-3-3 doesn't matter, playing principles is what defines the playing style.
Yes, but the formation also matters - it needs to fit the playing principles, among other things.
If we accept that the issue is the lack of balance and control in a 4231 with the four attackers doing little pressing or defensive work, then there are two possible solutions: Fewer players with a primarily attacking role, or more defensive and pressing work from the attackers.
The latter solution is compatible with any formation. The former dictates a shift in formation.
433 and a 3 at the back type formation, such as Chelsea's 3421, seems like the most obvious options.
With a 433, that would mean either forcing Bruno into a lower and more defined role in the midfield, with more extensive defensive duties and benching Pogba, or arranging the 3 man attack line so that Bruno can play in it, and use Pogba together with Fred and McTominay in a flatter midfield 3. Either way, there would be an awful lot of excellent players seeing a lot of bench time.
The more I think about a 3-at-the-back formation, the less I like it. Particularly in terms of squad suitability. If you want a 3421 formation to work in the sense of allowing you to control and dominate the game and produce steady offensive pressure, as opposed to just drop back securely and counterattack (which is a futile approach, as it is completely ineffective against most teams we play, who sit back and have to be broken down), then I think Tuchel's Chelsea give you the template for that: Tight cohesive shape and intensive counterpress over the whole pitch. If we can do intensive counterpress, then there's no need to drop 4231 in the first place.
Also, I think for such a formation to work, the three parts of the team that absolutely needs real, serious quality is the wing backs, the central midfield pairing and the striker. The striker because I think you'll tend to generate fewer quality chances with that formation, and so you are more dependent on a first rate finisher on top. We have that in Ronaldo, so that's fine. But then it gets more difficult. You're so dependent on the wing backs for any kind of offensive pressure, and at the same time they'll have a lot to handle defensively. The CMs, like the wing backs, have to be able to contribute a lot both with and without the ball. It's those four players who largely determine if you're getting pushed around or if you impose yourself with that formation.
And, those positions are where we would be weakest. We don't have a fully formed wing back other than Alex Telles, and on the right side it's an open question if we even have someone who would be fully functional, never mind dominant. And our CM would still be our CM. It might be an easier framework to perform within than our current formation, but we would hardly have a top class central midfield duo anyway.
For the remaining five spots, I think we'd be fine. A 3-man back line generally requires less from each CB than a CB pairing does, and makes it considerably easier to perform well. And the two attackers behind the striker, that can be done effectively in a lot of different ways and there's also no lack of players who could do that well.
All in all, I think that if we go that way with this squad, we'll end up with a more defensively secure team, but also one that is not able to control or dominate games, and which will be hugely challenged against weaker, low-defending opponents.
So I guess that brings us back to 433, or the forwards doing more work and doing it well.