I want to make Li-Ion battery supply to power a USB isolation board is a 2S3P configuration. I want to put an active BMS board on it. I have a 3S and a 6S BMS board. Will either work? How should I connect them to the cells?
It really depends on the BMS. Some can be configured to use fewer cells. I won't describe how that is typically done though. I don't know anything about the BMS you have and don't want to be responsible for you burning your house down.