The pecking order is indeed PPS Solitaire > PPS > KF Gold > KF Silver
PPS is higher in the pecking order as this status can only be achieved by flying paid J and F. You can get to KF Gold by only flying Y and even without ever having set foot on SQ.
If you are PPS and KF Gold at the same time, only your PPS status will be reflected (as it is the higher status), e.g. you will only have a PPS Club card.
Within the same level, the number of qualifying years gives priority. A PPS for ten years beats a PPS member of five years.