I never heard the Sea Princess as an R Class ship. We called it the Sun Class ships (referring to the old Sun Princess). The Pacific Princess (2nd), Tahitian and Ocean Princess (2nd) were all R Class ships. These were Renaissance ships, thus, R Class. Approx 30,000 tons.
The Sun Class had the Sun, Dawn, Sea and Ocean Princess. These were around 77,000 tonns.
I agree about Sapphire and Diamond Princess wide promenade decks. I don't remember the Coral Princess having that wide but it has been awhile since I have been on that ship.