I think Johnson wants to play with only 1 holding player this season. Just a theory. He has said he signed O'Nien to play as an 8 so I think he will be higher up the pitch when we have the ball, next to a number 10 and behind and attacking 3. It will be a really aggressive and attacking 433 I think with full backs that support as well. If 1 full back goes the other has to move over to make a 3 otherwise we are wide open. Evans will have a massive role to play when we lose it in terms of delaying. I think it is why full backs are a tough position to fill as we want those who can get forward but with rapid pace to get back.
Think when we don't have the ball the "number 8" will drop in alongside the "number 4" but when we do have the ball the number 8 will have license to move forward.
Formations aren't really worth much nowadays without additional context. So I agree with you, just think it will be fluid