Persistent world with UE4 (not an MMO)

This process exists, no matter how the data is saved/loaded. The application (UE4 Engine) generates (spawns) the actor (object) instance to hold the data, and the data is loaded from a local/remote source and assigned to that object. In regards, to how many actor types is a matter of actor design, the actor can be complex or simple. I personally use Arrays of User Defined Structures to store my data, which maps easily to Data Tables, which I can further format the data into SQL strings or serialize in JSON or XML.