What options are there to limit which routers OSPF neighbors form with? I am aware of limiting interfaces (via "Passive-Interface") that participate in OSPF advertisements, but I was wondering if there were other / more efficient options ---> especially in a router with many interfaces.
"It sounds like with just the network statement as we have it, we are hitting our goal and we don't need the passive-interface - is that true? "
Correct. OSPF would only use the one interface, if you configure the network statement's mask as I've described.
"passive-interface" might be used if you had placed an interface into OSPF but didn't want to peer with other OSPF neighbors. For instance, on a user facing access subnet, you might use it as one of the methods to keep your router from peering with a user host PC running OSPF and further not even send hello packets that could be sniffed.