Does anyone know if there is a system report that can be used to show all emails sent from the platform as well as classified as either being in a journey, user initiated, or from automation studio?
Short answer is no.
Long answer is that there is a report for all emails sent (Account Send Summary), a field to show if they originated from Journey, UI, etc. is not included. You would need a lot of stored info (to designate origination) and SQL queries (pulling from the data) to accomplish this. There is nothing built in that I am aware of.