The main difference from what I gather is the intensity of the mania.
BP I has full blown mania, which often requires hosiptalistation.
BP II has more hypomanic episodes, that is not quite full blown mania. It still includes racing thoughts, increased energy, less need for sleep...

But only a psychiatrist or psychologist can really make a diagnosis.

I'm BP, and also spend most of my time in depressive or mixed states. I've never had full blown mania either