OK. Playoffs in OOTP6 are customizable, but not fully so. In my fictional solo league, under League Setup, I can click on Playoff Structure and choose between:
1. No playoffs - self explanatory
2. Round 1 and Round 2 - Winner of each division advances to playoffs
3. Round 1, Round 2, Round 3 - First 2 teams in each division qualify for playoffs.
Like I said, this works on my fictional league, which has two leagues of two divisions, each containing 5 teams. I assume that the options would be different for leagues of a different structure, but I don't know - I haven't tried it.
So, in short, yes, there is customisation, but it is limited, probably depending on the structure of your whole league.
Oh, and you can also edit the names of the playoff rounds e.g. instead of LCS, you could have 'Regional Championship' and instead of 'World Series' you could have 'Australasian Cup'. And you can edit the amount of games in each playoff series - either 3, 5, 7, or 9.
So I think it's quite nice.
