Even though Kylian Mbappe doesn't get as big a salary as when he was at PSG, at least Mbappe's future will be bright at Real Madrid and Mbappe has the opportunity to get the Champions League trophy with Real Madrid which he can't get from PSG because there is little chance for PSG to get it because of the good players they have PSG only has Mbappe, while at Real Madrid there are good players who can work together solidly and Mbappe can be helped there to win individual trophies and also major trophies.
Going to Real is clearly a great opportunity for Mbappe to win titles. But in return, he had to sacrifice many things, especially his own ego. At PSG, he was considered a king, an untouchable forbidden zone, but at Real, he had to lower his ego to integrate with other stars. I think that's also the reason Mbappe is considering, Mbappe is not the type of player who can easily integrate into any team like Ronaldo.
Real madrid needs to hire him caused by the club needs to have more winger to play. Vinicius was often injured and this is gonna be the key point to recruit mbappe to join in the club. I hope that all of process will be going very well.
I think that both Mbappe and Vinicius will probably play together and one of them will swap positions between wing striker and center forward, both of them can do this role well. And of course, if one of the two is injured, the other will return to his strong position as wing striker. The addition of Mbappe can bring a more varied playing style to Real and is also a backup plan for the wing striker position.