Hey there,
It will not be the typical and very specific McK PEI that lasts for 15 minutes and only covers one story: https://www.preplounge.com/en/mckinsey-pei
However, you will be asked similar questions and are expected to answer them in a more succinct manner (also the interviewer does not drill down as deep). You will never only have one question in the fit part of BCG, but a sequence of rapid-fire questions and some more detailed ones.
Cheers,
Florian