Coman didn't even own Alves like that. The one time he got Alves was on a counter attack when he just beat him to the ball because Coman might legit be the fastest winger out. Dude has much more blistering speed and acceleration than Sane. Sane is not better by much and City would have most of the possession if they play and he's not technical like that to get past Alves in a set defense. On the counter, maybe. He's fast but he's not Coman fast.
As for Neymar showing Alves mercy, you gotta do better than that. How come he didn't show his cb countrymen mercy when he wash PSG at the return leg?
City won't have 60% possession against PSG. Will probably be 55-45 so City will have some opportunities to counter attack.
This is all hypothetical though, PSG need to get past Madrid, which I don't think they can.