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.