Here is a demonstration of the dynamic spawning aspect of the random prop manager. Functionally it is similar to setting max draw distance, but the trigger box can potentially be customised so that actors are only spawned when in appropriate sight lines.
One example of customised triggering is the 'on entry' spawning method, whereby actors are only spawned if a door is opened or a threshold trigger passed. This will probably suffice for most of the props in a particular building (especially upper floors). This system was envisaged as being useful especially for large blocks of flats.