Mbappe at Real Madrid will make Real Madrid's performance sharper and the opportunity to win the Champions League title is wide open because Real Madrid's attack line will be stronger, but it's true, as you said, anything can happen because we also can't be sure what next season will be like. Either Real Madrid's mainstay squad will be in good health and not suffer any injuries during the competition because if one of Real Madrid's mainstay players is injured it will affect their performance and it will also affect their chances of winning again.
It cannot be denied that another reason he moved to Real Madrid was that he wanted to win lots of trophies and the pinnacle of his individual achievement was the Ballon D'or, and that was very natural because he was a talented young man. My prediction is that Mbappe will quickly adapt to Real Madrid's game because he fits very well into coach Ancelotti's scheme with players who have high speed.
You are right I also agree that Mbappe was under a lot of pressure when he was at PSG. However, it can be argued that Mbappe is very happy at Real Madrid at the moment and it will be very interesting for him to fulfill his childhood dream. Of course now in Real Madrid Mbappe will play and he will not have to take so much pressure but he will be free of pressure, also we have seen before in PSG to be disciplined and under pressure but now in Real Madrid he will not have to be under so much pressure. And I believe Mbappé is still a young and dynamic player who will definitely contribute well to Real Madrid. Moreover, he will definitely be able to improve his career at Real Madrid and have a chance to win the Ballon d'Or. Mbappe will now be with Real Madrid with his full talent and make the team even stronger. Moreover, if he can adapt to the coach and players of Real Madrid, he will definitely be able to improve his career in the future.