Since there are only two routers on a point-to-point link, there is no need to hold an election for a Designated Router (DR) and a backup DR as OSPF would in a broadcast network.
An OSPF router on a point-to-point link will multicast its OSPF on the link for the other end to receive. On a point-to-point link, a router can only establish one neighborship.
A loopback interface in OSPF will be in loopback mode. Setting OSPF to point-to-point mode results in advertised routes containing the actual subnet mask instead of the default behaviour of advertising /32 for a loopback interface.
Iirc I read something about scenarios in which advertising a /32 instead of the actual mask causes trouble. I have only ever used this to start advertising a network that was not yet attached to the router.