Would suffer from the same in-game issues Dembele has so far. He is built for counter-attacking teams.
I don't know much about Sarr, but Dembele's problem is that he's always been a player that's stands at one place and waits for the ball so he can carry it. If I had the footage I could literally make a comp of Messi or some other player telling Dembele to move his ass into the right positions as the dude just stands at one place ball watching.
If Sarr is more of a runner/player that's great off the ball he would be a way better fit. Not that I would sign him though, definitely not based off on one game.
We don't need creative wingers or wingers that absolutely need to carry the ball and touch it a million times to be effective. We need players who can get in behind with pace, beat a player 1v1 and finish chances.