4-3-3 with the best under 23 players. To find out who are the best players at each position, I took in the age, overall, and potential of the players in a formula ---> [(Overall + 4 x t in years until 23) + (Potential + 2 x t in years until 23)]/2
I might have missed some players but even if I did the team should be very similar to this one.

GK: - Donnarumma = 95
- Vandevoordt = 92

CB: - De Ligt = 97.5
- Gvardiol = 94.5
- Rensch = 94
- Nianzou = 93
- Kana = 93

LB: - Saka = 97.5
- Davies = 97

RB: - Alexander-Arnold = 95.5
- Dest = 93.5

CM: - Camavinga = 101.5
- Pedri = 101
- Wirtz = 100.5
- Bellingham = 99

CAM: - Reyna = 99.5
- Cherki = 99.5

ST: - Haaland 101
- Fati = 101

LW: - Mbappe = 98.5
- Hlozek = 98.5

RW: - Sancho = 98
- Greenwood = 98