I am not sure how to rate sheets and blankets, but I do know I sleep well. Perhaps someone will be able to give you a thread count. We have cruised with Princess many times.
My wife does bring her own pillow because she does not like the pillows on the ship. I have never heard her complain about the rest of the bedding items.
I hope this little bit of information is of help. Have a great cruise.
Like Irvine Traveler, I can't give you specifics; but we have been on many Princess ships and have always loved the bedding. The last few ships we have been on have gone to duvets instead of the traditional sheets and blankets. The first time I saw one I very ignorantly said, "hey, the steward forgot the sheets."