I suppose it's worth keeping in mind, like Wcs said. But I think what it comes down to -- and this is always a thing with any amateur or pro league -- is what kind of numbers the league's top scorers put up. So, like, Rossi's 120 points is probably inflated; he's got a clear age advantage (late September birthday) and that's going to help him even if poor OHL goaltending isn't a thing. So let's subtract, say, 30 points. Even with 90 points, he'd still be in pretty good company:
https://www.quanthockey.com/ohl/en/seasons/2019-20-ohl-players-stats.html
TBH, I'm not interested in Perfetti. I'm very high on Rossi tho. He's an Yzerman type, i.e. a smallish, high-skill, high-IQ, hard-working, well-rounded playmaking centerman who plays in the guts of the game across all three zones. He's always impacting the game, making things happen.
This is a good profile that goes over Rossi's numbers (and more) in detail:
https://www.silversevensens.com/2020/6/1/21276461/2020-nhl-draft-profile-marco-rossi-ottawa-senators-nhl-ohl