Maybe Harry will be the best player in this tournament because of the more potential they have in Bayer Munich and we know Tuchel joined Bayer Munich to help them win the Champions League after years. That's why I think Bayern Munich got more chances than other teams like Manchester City and Real Madrid in this tournament.
Do you mean Harry Kane could become the best player of this tournament in terms of the number of goals he can score or from a more general point of view, like convincing performances regardless of the number of goals scored?
If we look at the number of goals, there is still Haaland who I think will most likely be the strongest competitor for Kane to become the top scorer of this Champions League season. And there is also some luck involved as it makes quite a bit of a difference against which teams you are playing in the round of 16, quarterfinals, then semifinals and final.
Rasmus Højlund is still at the top of that list for Manchester United, but his great individual performance didn't help much. It may help him as other clubs will keep an eye on him and if Manchester United fails to qualify for the Champions League next season, I think Højlund will reconsider his engagement with Manchester United and express the desire to leave the club if some other top club is willing to pay whatever Manchester United will ask for.