I think Fati could play up top too, whereas Johnson seems like a pure duel with Kulusevski for RW minutes.He's a left inside forward, and we plenty of left-sided players already. He also has one working knee and is not as athletic as Johnson.
(The 4-4-2 in the second half last night was interesting, I didn't know Ange had that in the bag, could Johnson partner Richy/Son up there? Would he play a league game with Bissouma and Maddison in a *gulp* diamond?)