Sounds like you have the most wonderful trip ahead.
I have stayed at both the hotels you mention in krabi.
My own view is that rayavadee is awful. The most disappointing luxury travel experience ever. Yes stunning location but still surprised that people think it's worth the premium. Run down and over crowded is not the right word. My advice is go for a day trip with the other 16000 day trippers.
Ritz Carlton PB is wonderful but not the best beach, that said I did not want to leave this place. Quiet peaceful and stunning. Dining is limited but there are restaurants 10 mins by taxi. There is also a wonderful beach 5 mins away which is deserted and perfect white sand. No hotels and no people. Ask PB and they will direct you to it.
I note you did not consider Khao lak. Also worth a trip if krabi falls of your list.
Envious and may need to book a trip myself now thinking of the sublime beauty of Krabi.