You log both P1/PF and P2/PNF hours, and the total of these needs to be 1500hrs
However, you must have a certain number of P1 hours (300 IIRC). Some of these can be PIC U/S (under supervision) which is co-pilot time in which you are PF, against which the captains signs your logbook. This is about the only useful application of the PICUS term - the reality being you are either the PIC or you are not, end of story.
You can also count up to 100 hours sim time towards the 1500 required.
The bottom line is that there is no such licence as a "frozen ATPL." The term is merely a marketing tool implying you have done some exams. You either have a CPL or an ATPL.