Suggest you read this documentation on visit_occurrence, it is for CDMv5.4, but also applicable to 5.3. I do not believe there is a one to one match between and Epic episode and the OMOP definition of a visit. For example an inpatient visit with follow-up telephone calls should, in OMOP, be separated into two Visit Occurrence records, one for the hospitalization and another for the telephone follow-up (if you care to record that information).
Another way to help you in deciding what constitutes a visit is to think about how your OMOP CDM will be used. Visit type is often used in selecting cohorts of patients. A researcher may only be interested procedures performed within a hospitalization.
“…and that the best way to represent them is to have one row per VISIT_OCCURRENCE_ID/VISIT_CONCEPT_ID, and treat that as the primary key” Not so, make these into separate Visit Occurrence records.