Osimhen is a quality striker, there is no doubt about that. I don't think he is the primary option for Real Madrid. Haaland would be a great option for Real, but my preference would be Mbappe. He has a structure that can play both as a forward and as a wing. Haaland plays as a complete finishing striker. While Mbappe makes it easier to intervene in the game, you cannot remove Haaland from his position.
If Osimhem is the striker that Real Madrid is targeting then in the previous transfer market Real Madrid will definitely make an offer to Napoli and I'm sure it will be difficult for Napoli to refuse that offer. But in fact, Real Madrid did not make Osimhen their main target and still favored Mbappe as one of their desired targets. Mbappe has much better advantages compared to Haaland because this typical player is much stronger and masters playing positions on the wing or as a central striker.
Haaland is only able to complete passes to score goals, but speaking of needs I believe Haaland and Mbappe are two figures that Real Madrid really needs. If both of them can be brought in in the next transfer market then I think the Real Madrid squad will be much better and will produce striker who are quite feared by any opponent.