Barcelona will definitely release their players if they don't want to be caught in sanctions. But there is no certainty who the players will be released. Aubameyang will not be released because he was bought from Arsenal by Xavi Hernandez. Frenkie De Jong has the opportunity to be released to Chelsea because Barcelona are still holding out a deal with Manchester United for the De Jong process.
And Chelsea will be better and stronger if they manage to bring De Jong into his current team with a wiser deal than Barcelona. I'm also still waiting for it to happen because there are still a lot of rumors and news surrounding De Jong about this. For Manchester United I think it is better to look for other players than to wait for clarity from Barcelona for De Jong.
I think without De Jong, Chelsea's midfield is already very solid under Jorginho and Kante's control. But if they manage to buy Frenkie De Jong it will make Chelsea stronger. Their chances are bigger than other clubs.
Chelsea must focus on attackers, because that is the position that is now in the spotlight. The centre-forward should be the main target for not relying enough on Sterling and Havertz considering there is some competition played by Chelsea.