I think in an ideal world the youth teams would play in a style defined by the club and the first team would play the same way. This would be defined by the director of football. That way when the player moves from u23s to the first team, its the same formation and same style of play. This is the basic principle at Barcelona and and Ajax, but i dont think many clubs do this in the premier league, most of the players that make it from u23s to first team do it because they are so much better than the kids at that level or they go on loan in the championship and prove themselves