If a formation suits the majority of your better players but means one plays slightly out of position I would go with that. I think Powell has had some of his best games playing on the left of a front three the season before last.
And if a formation (such as 4-2-3-1) suits all of your better players and is the best formation for your best player, that should be used. It’s madness to have one of the best 10s in the league and want to play that 10 on the wing or as a striker.
For me he is a very poor man's version of Benzema. He could play as a CAM, but he's best as a CF because he can better occupy a defender than make use of the space.
In a front three with him, Campbell and Brown he can drop a little should he feel he needs to get more on the ball.