I don't see a Peter Forsberg comparison at all. Kakko doesn't seem to have the reckless abandon physical style that Foppa had. I also think Kakko is more of a scorer, Forsberg was typically more of a passer and two-way player. He only ever hit 30 goals twice in his career. Kakko is bigger and drives the net and scores more.
He is kind of a do it all sort of forward. Looks more comfortable on the wing but can play C in a pinch. Closest comparable I can think of is Patty Marleau. Good speed, good stickhandling, drive the net, create chances, big and can play physical but aren't the in your face physical types.