What exactly does a public trust clearance investigate?
Depends on the level of classification. For a low risk classification, there is no formal investigation. For a low sensitive level, they do a NACI check which doesn’t require a formal investigation. For a moderate risk level public trust, it’s a more involved investigation that will involve an interview and completing an SF85P form that delves into your life a bit more very similar to a T3/secret investigation based on an SF86.