I am very sure Nico will be successful in Barcelona, especially since this team is like a second home for him because many Spanish national team players play there, plus Hansi Flick magic hand has proven to be very good at bringing out the talents of young players,
Nico Williams is tailor-made for Barcelona and the kind of football Hansi Flick plays. He's fast, good with the ball on his feet and knows how to run at defenders and force the attack. He is the perfect fit for that position in the long run. His numbers are the only poor part of his game, but I believe in a team like Barcelona, where they constantly attack, I believe his numbers will improve.
so the question is if he plays in Barcelona, which position will he fill? The left wing already belongs to Rafinha, this one player is difficult to replace, the right wing? This is like shifting Yamal position, maybe it will alternate with Rafinha and Yamal, which is also good because Barcelona does lack players in both positions.
Raphinha is not naturally a left winger. In fact, last season he didn't even play the left wing. It was like that on paper, but on the field, he usually drifts to the middle and has almost a free role on the field. He could totally play the free role because he had to maintain the flank.
With Nico in the team, Raphinha can play behind the striker and have a freer role on the pitch. He can also act as a second option to Yamal's position, which is his natural position. I don't see an issue here at all.