I saw no one responded to your question so I'll give my experience with mixed episodes.

For me, the best description was a really agitated and severe depression. I think mixed episodes look different for different people. In my case, mixed episodes were times my depression was most severe coupled with the energy and agitation to act on that depression; thus, they were highly dangerous for me. Each and every time I was hospitalized, I was in a mixed episode and highly suicidal with the energy to act on it.