It's hard to compare across managers and systems. I think the idea that there's a right footed player that can cross the ball from the right is fairly well accepted. Ever since inverted wingers became a thing and fullbacks started to come into the midfield, that cross was increasingly being played by the midfielders. The trademark KdB ball from the right is a pretty good example. Bruno did that last year for us when he was more biased towards the right wing. It doesn't have to be the fullback providing that delivery. I think the nature of the delivery also changed a bit -- now it's more the cross from the half space.
The problem for us I guess is that both Amad and Dorgu are left footed and that throws the balance off. Let's see how it's solved. The balance does look better when Bruno shifts over to the right, Amad to RWB and Garnacho as the left #10. Note that in this case (Amad at RWB) you still have a left footer at RWB.
I dunno, I think it still makes sense in a 3-4-3. The attacking shape is still a 3-2-2-3 (or 3-box-3) regardless of whether you arrive at it from a 4 ATB or 5 ATB. Ultimately there are a list of attacking patterns you want to achieve like ball goes wide and is passed inside to the man in the half space. Ball goes wide, player goes down the touch line and crosses. Ball goes wide and player provides cross from deep. Ball goes wide, player dribbles and cuts in with ball, another player occupies position to continue to provide width etc.
I think it's a bit fluid who does what in this case.