It will be difficult for Chelsea to get Nico Williams, the competition for him is too high and Chelsea at the moment cannot even guarantee him participation in the Champions League. Osimhen's move is quite possible, although he has a high salary, but he is worth it. The question is whether Chelsea will be able to agree with Napoli, which seem to hold a grudge against Osimhen.
Nico Williams is essentially one of the great players in Athletic Club. His presence matters and there's every tendency for the club to beckon greatness this season. They're important phase in the semi final of the Europa League. I don't believe news that tangled Chelsea with uprising talents in Europe. We all know the scouting sector of the Blues, they're incompetent and not making good decisions when it comes to signings.
Chelsea have missed out on big chances in the past and I see no difference for the club currently, they can slowly fade away because they're not making good signings, immature choices ruined their form and make them decline in performance. This is not just a good reason for the club to be far behind.
As far as I know Nico Williams has an undisclosed release clause or if somebody else knows it maybe you can add it to the discussion here. His contract expires in summer 2027, which gives Bilbao one more year to say no, but other clubs are aware of that and Chelsea has the financial means to get Bilbao moving and let him go.
Because of this great season for Bilbao, they have something going for them as they are participating in the Champions League. That's one big aspect that players have to consider when they want to make the next step in their career and Nico Williams is ready to take that step, but if he can do it in Bilbao, play on the highest level and keep developing for one more year with another great season, it could pay off for him.
But as you know, these young guys from today usually don't show much patience and want to go elsewhere once those clubs knock on their door. Regarding Chelsea, I think it would first have to be sure that they play Champions League. Otherwise there is no reason to join them.