Kakko's play along the boards with his ability to pivot, stickhandle around opponents and protect the puck with his frame remind me a lot of Gabe Vilardi.
Kakko has good, but not great straight-line speed -- better than Vilardi does -- but his edge work and ability to retain the puck after eluding defenders is excellent. He plays a European-style power forward game, comparable to Filip Forsberg and Vilardi in a lot of ways: he isn't going to overwhelm the opposition with brute north-south strength and speed or physicality, but has the size, balance, agility and puck skills to protect the puck and maneuver with it in tight spaces. Raphael Lavoie is that speedy, aggressive power forward type.
He hounds the puck and plays a patient possession game, fighting to keep the puck when the opposition is draped all over him in order to open up teammates for pass or create a chance for himself; he'll also carry it around the zone if he sees space available to put himself in a better position to make a play.
There is some great footage of him from the 2018 U18s. bigwhite06 (Feebster on HF) and a new channel called Hockey Prospects Center both do video packages that are more than just goal/assist highlights; rather, their videos show the player's best plays, from takeaways to scoring chances to great passes as well.
I find that Hockey Prospects Center's Kaako video is more tightly-edited, with more plays shown and fewer replays of the same clips; both videos overlap in terms of a lot of footage and are about the same length, but this one flows more quickly -- video isn't quite as crisp as Feebster's, though: