Olympic system, BO1. Starting from the quarterfinals, BO3. Grand final, BO5.
It would be better to do the opposite, giving more opportunities to play to all participants, and fewer to the top players. I don't think that in a match between players like Redi_Hell, the probability of either winning will change depending on whether it's BO1, BO3, or BO5.
Therefore, I suggest BO3 in all stages.
Initially, 3 weeks will be given for the first round, starting from the quarterfinals - 2 weeks.