I agree with Chaley,
Nice router 
and one of the nicest users guides I have seen so far. They did not forget (my pet peave) to include the screw hole template for those doing (high up) wall mounting

I am not sure why connecting storage to the router would be much different than elsewhere on the network. Because of no A/V?
I would check that the Guest account has a
different SSID and Password

The Status section in the Routers configuration utility will show which SSID's are in use by devices