P1S is supervised PIC which is only done in intergrated flying courses.
PICUS: is PIC under supervision which can be logged with permission of the Captain (I know most folk don't bother but some will get in a right tizzy if you preseum you can) on your sector if you carry out all the dutys of the PIC and don't cock it up. Some countrys have different ways of doing it. It is also logged on completion of a passed flight test.
PIC is only when you are responsable for the aircraft and sign the tech log.