The game will be win and lost on how Barca deals with Psg pace on their wings.
Araujo will have to move over to nullify Mbappe. Inigo can come in at centre back as Psg have average centre forwards in Muani and Ramos. It's unlikely Barca get punished there.
That leaves Cancelo Vs Dembele. Dembele will skin him for pace a few times but as we all know , there will hardly ever be any end product at the end of it. Just need to double watch cut back to Mbappe when Dembele gets free. Ideally, would have Balde there for his pace but that's not an option.
Fermin must play for his goal threat from midfield as Barca don't have it up top, bar Lamine. His long range sitting will also help, as Donnarumma is prone to a clanger or two.