The majority of the best teams in the world ie City, Liverpool, Madrid, Bayern play with a “normal” back 4. Chelsea, Spurs, PSG play with a back 3. Chelsea and Spurs are both teams who tend to play on the counter in big matches so it works well for them in those scenarios, we’ve seen how many times Spurs seemed to have turned City over in the last few years and obviously Chelsea’s CL win.
Have a look at how Xavi sets Barca up though, 3 at the back with 2 holding midfielders and essentially no wing backs then more of a “4” behind Lewandowski. The “wing backs” if you like are Dembele and Torres/Pedri, players who are very attacking and end up playing either side of the striker. Must have bollocks of steel setting up like that but I’m all for finding out how it goes because I think he’ll one of footballs great managers.