I don't think Lafreniere ends up a bust, but he's not going to be the guy he was hyped. People gave way too much credit to his skill level and didn't look enough at his early physical development being a key reason he was so good in juniors. If he ends up in Chicago as a part of the Kane deal, I think he rounds out into a solid 1st liner in a Landy sort of mold.
Now Kakko scares me a bit more on the bust train. I say this while acknowledging he's been very good in December, so a corner might be getting turned. That's a guy who seemingly has zero idea what to do when he can't over power players. In the NHL he's a below average skater with pretty average strength... he can't physically dominate anymore and without that, he doesn't have the IQ or skill to be a high impact guy. Add to that his shot has messy releases that goalies can easily read. I simply don't see the high end upside right now. Maybe in time you get a good 2nd liner who might get you 60 points with 30 goals... you might only get a solid 15-20g 3rd liner though and as a #2 pick, to me, if he doesn't hit that 2nd line level... that's a bust.