I did a little more offline testing with this newfound knowledge and discovered…
Ken's island resort today:
26 FPS https://i.imgur.com/STl1acq.jpg
Ken's island resort with no item frames:
65 FPS https://i.imgur.com/MkKAGb4.jpg
Ken's island resort with no item frames and chests replaced with barrels:
92 FPS https://i.imgur.com/Hw2vVQZ.jpg