Personally, I'm not sure to be honest. They seem like a team that's bought a load of players that are available rather than a team with any strategy about what they need. If I look at the players they've bought...
Messi - best player ever for me, but 34, and was scoring goals really their main issue? They could barely get the ball off us in the CL.
Wijnaldum - decent player but is he really turning any midfield from decent to world class?
Ramos - 35, played 15 league games last season, lost his international place. An experienced head, but it's not like they've signed VVD or Dias.
Donnarumma - incredible free signing, but was goalkeeper a weakness for them? They've got a great keeper for years there, so it's good long term, but I'm not sure it's massively improving them in the short term.
It seems to me like Pereira and Hakimi were signed with a plan in mind and the rest was like a kid in a sweet shop just signing any big name who's available on a free. I guess we'll see, and chances are they'll win Ligue 1 anyway, but the CL will be the real test.