I'm a little late to the party. But after this past 20/21 season, he looks like a surefire 1st line winger to me and almost certainly one of their best 3 forwards. Maybe eventually their best, or top 2 forwards.
Comparisons: lol. Selanne? Ok realistically he won't reach Selanne level. Iginla and Recchi going too far? All around 6', Recchi a bit smaller. Maybe the closest comparison of the 3 though. A bigger Theo Fleury? If he truly reaches his ceiling though, I am not sure Iginla LIGHT is out of the question. Patrik Elias? But I'm going with Recchi comparison for now. And he's about 2 inches taller than Recchi. And Recchi was a grinder, all heart and was everywhere on the ice. Farabee isn't quite as fast as Recchi, but still, fast enough. These of course are "best case" scenario.
Guentzel seems a decent comparison for current NHL players though. Maybe a floor of like Perron.
Either way, he's a future all star caliber player. Maybe not a guy who gets selected as an All Star every season, but always in contention to be at that level. If they pair him with the right center, and wing partner, the sky is the limit. I think all ready as good as Konecny, and getting better.