multiplayer map loading question

I am testing (early) work for multiplayer, but I don’t understand how the client travel works. When I start two PIE windows I see one is the server, one is a connected client. Both open the persistent level, but then the server proceeds to use some logic in my gamemode BP to decide which of several streaming levels to set as “should be loaded” and “should be visible”.
My questions: Does the engine automatically replicate sub-level streaming, or do I need to create some events and logic to do this myself? If I need to do it, where is the “best place” - I seems that my gameMode BP is the suggested spot for level loading logic, but that won’t exist on the clients.