The number of rounds should be (at least) log2 X rounded up, where X is the number of teams.
Any less than that, and the best two teams (or worst two teams) may not play each other, and more than that, and you will end up with teams playing other teams which are futher away from them in the ranking, producing mismatches.
Up to a point that doesn't matter too much, for example with 32 teams, you should have 5 rounds, but with a 6th round, worst case 1st plays 7th, and 32nd plays 26th, which shouldn't be that much of a mismatch.
The number of rounds should be (at least) log2 X rounded up, where X is the number of teams.
Any less than that, and the best two teams (or worst two teams) may not play each other, and more than that, and you will end up with teams playing other teams which are futher away from them in the ranking, producing mismatches.
Up to a point that doesn't matter too much, for example with 32 teams, you should have 5 rounds, but with a 6th round, worst case 1st plays 7th, and 32nd plays 26th, which shouldn't be that much of a mismatch.