Not sure what to say (Garycon crud gave me fever so I’m even dumber than usual) but:
I’m not sure whether you like third agents in the sandbox. Usually I have several faction/Gangs/whatsits do things at the same time as PCs, and the PCs can decide to interact, ignore, evade, suffer the consequences. This approach to agency is what makes pbta games completely useless to me.

As for the latter: I’m not sure. What of there is a secret that the players do not discover? Why putting it there in the first place? But if it can’t be discovered, it’s mostly useless unless it provides utility to a third party.