Both them going would be a non-issue. We already have Martial (better as a striker than winger) and Rashford.
Personally, I would prefer a more balanced striker, operating in a similar role to how Firminho plays for Liverpool(think OGS will want to play similar to how Klopp and Liverpool plays). Among our current players, Pogba is the only one with the skillset to perform in this role. Greenwood with some muscles and experience has the skillset to play in all attacking roles and could be very well suited to this. Griezmann could do it, but doubt he is willing to come here without CL. He wants to win now.
Given the difficulty of finding these type of attacking players, we should aim for a player able to hold up defenders, win duels and able to press and create a better working environment for our inside forwards/wingers. Two options are Tammy Abraham and Sebastien Haller.
Haller is more technical and "tanky", while Abraham is harder working and more mobile. Both know how to position themselves before a cross (unlike Lukaku) and how to use their physique against centrebacks. If we could convince Chelsea to sell Abraham for £30m then we should be all over him. Seriously underrated player and he knows how to score goals. Would start neither against teams clearly better than us like Liverpool and City and the likes, as we would be better served by playing counterattacking direct football.