Going by DSM requirements, the psychosis has to last 6 months to be schizophrenia, schizophrenia symptoms that last from 1-6months would be schizophreniform disorder, under a month would be brief psychotic disorder. The psychosis in schizoaffective has to be 2+ weeks without overlapping with moments in a mood episode.
It's generally considered that when it comes to functioning schizophrenia<schizoaffective<bipolar. I'm unsure about insight when it comes to each disorder, but it would make sense that the average schizoaffective patient is more insightful than schizophrenia patients. I would say that's a generalization rather than rule though.