Liverpool has't stopped yet. They're trying to hunt more talent to be recruited. They have done with Frimpong, Wirtz (medical check up), Kerkez, (still in the negotiation), and add Isaak as their last target. Their target to sign Isaak from Newcastle is just getting even more possible with Nunez who is still in the process to go to the Napoli(i expect him to play for that italian club).
I think we will see Isaak to wear Liverpool's jersey as he has open the move to the any big club that play in UCL.
He needs no introduction is what Liverpool hopes for, but I think players like Isak and Wirtz still can be risky, they are not Messi or Haaland or Ronaldo. You could see that Mbappe had some problems when he arrived in Madrid. It was not like he immediately played his best game. I think Wirtz will need some time because he was perfectly put to use in Leverkusen's game and the game was made for him while the competition on his position was limited there. In Liverpool he will be a beginner like everyone else and he has to prove himself. The same is probably true for Isak.