Griezmann isn't just a finisher, he's far more than that and there is a reason why he and Pogba struggled to gel together for France, because it was two main men trying to fight it out for whose the boss of the French team and whenever Griezmann dropped deep to link up play, Pogba went into his shell and couldn't play his natural game. Obviously in club football and training together regularly, that dynamic would change and they can grow together and get the best out of each other but in the international football environment, either you click or you don't and you don't get much time to develop chemistry with team mates.
Silva and Griezmann wouldn't work at all in a Jose Mourinho managed side, he'd be utterly clueless at making those two work together.. I can just imagine it being so one paced, with us once again heavily reliant on Valencia making that right flank work whilst Silva, Griezmann are both in central areas just outside the box. It wouldn't be awful, but it wouldn't be successful and very easy to defend against. Mourinho doesn't have that super attacking brain where he can make gold out of players with bad chemistry, whereas give Pep possession players and he can make them all click and create a cohesive brand of attacking football. Further more, he fully commits to possession football which gives these players confidence to play their natural game no matter what whereas Mourinho lacks that patience to make it work.
Mbappe is not a pure 9 yet, he's a wing forward, support striker, 9 rolled into one at the moment and from what I saw from the Juventus game, he'd be a great wing forward with licence to roam and if he could cut inside and switch up with Griezmann as a false 9, or even the two of them up front in a diamond it would be devastating and much more penetrative than a team with Silva out wide.