Real Madrid is doing their best to improve the team, even though they are already pretty great. But the real problem they have will appear at the three wings they have. Last season they played with Vini on left, Rodrygo on right, and Mbappe at striker.
This season, there are two main issues. One is that Xabi wants to play with two upfront, which means they will have Vini on left and Mbappe on right striker. That means Mbappe will play out of position, while he is still good there, he will hate playing there, and that is number one problem. Second is that Rodrygo is a level of player that needs to play every game, he is not a bench level player, so to see him at the bench, means Rodrygo will hate that as well.
I think Alonso will change the system, because I don't see him finally deciding, at the Club World Cup he played with three forwards, Vini, Garcia and Bellingham, then Mbappe was injured and Rodrigo spent almost the entire tournament on the bench. Now Bellingham will be absent for some time after surgery, but he will still have enough attacking players to play even with three forwards. If with two then it is even easier, the most important thing now is the midfield.