(Just saw it's a duplicate with https://bugs.mojang.com/browse/MCPE-111547)

Since the release of 1.17 I only have a maximum of 40 FPS in built-up areas. Several Minecraft and Nvidia updates have been released in the meantime, but none of them fixed the problems.
Before 1.17 I had 250-500 FPS without vSync.

Update: I was able to fix a few of the performance issues by removing signs, item frames and armor stands. The game runs better as a result, but is usually still far from 60+ FPS

My PC Specs:
CPU: AMD Ryzen 5 2600
GPU: Nvidia GeForce GTX 1660 super
RAM: 16 GB Corsair Vengeance LPX@3000MHz