I personally never do get interface with topology, as that would reset it all to what fw "thinks" should be defined...its way safer (in my opinion) to do without topology and as long as you set it per routing option, you are good to go, since if something changes on that interface subnet, no need to do anything, it would update it for you.
Below is what Im referring to and its always good idea to assign the zone as well.
Also, in simple words, anti spoofing is there so say if interface subnet is on 10.10.10.0/24 and traffic comes from 192.x.x something, it would get dropped.
Interface - Topology Settings

Best,
Andy