I primarily use the Loopback connector to manage workgroup membership. You can also use it to manage Capabilities, but I prefer to not assign those directly… I use workgroups.
I haven’t ever really thought about what the consequences of setting a user to Inactive will mean; does it mean the user can’t log in, even with a proper login? What you mean by “disable” I am going to assume is “prevent user from logging in”. There’s no lock or unlock on the Identity, that concept applies to target application accounts, such as LDAP / AD accounts.
I just ran a quick test using my sandbox, where I set the Inactive field to be editable and then set a user’s Identity to inactive. I was still able to log into that identity using the (still enabled) active directory account. That’s mainly because I am not setting a target on the inactive field. I wouldn’t recommend using a synchronize (target) setting on inactive; I would rather use a workflow. I almost always have inactive=true meaning call the Leaver workflow.
Not sure if this answers your question, feel free to tag me. I don’t get on this very often (I tend to spend my time on paying work). Tagging me will send me an email.