Well Nkunku is a good option, because Aubameyang is a very good player and he needs help, I see that Chelsea is a team that is getting very in tune with everything, Poter is undoubtedly a very good manager, some criticize him a lot, but I think Nkunku is the perfect choice, now we have to wait, I don't know if now they only have Nkunku in view, as I see it I think there may be other player options, when Aubameyang played for Barcelona he did so excellent, for me it was a mistake that he left, this is something that I don't know how Xavi thought of releasing it, but hey, everyone decides how their team will go.
Yes, Aubameyang is a good striker, he already proved it in Dortmund, in Arsenal, and in Barcelona.
Although he played for a short time in Barcelona, he can show us that he is a skilled and talented striker. He scored some goals in important matches and become a player who contributed very well. When he was in Arsenal, he becomes the club top scorer, too. No doubt that he is a great striker. Now, he only needs more time to show his contribution in Chelsea, he also needs another striker who can help him to optimize his potential. Sure, Nkunku seems fit with Aubameyang and Chelsea squad.
About Aubameyang leaving Barcelona, I don't think it is a mistake made by Xavi. Xavi knows that they have Lewandowski, it is not necessary to have Aubameyang too. Aubameyang must be unhappy sitting on the bench, he needs time to play regularly. So, to minimize the conflict, Barcelona prefers to sell Aubamayang.