Basically i had a world in 1.17 with caves & cliffs experimental toggled on and it was very smooth and operated as expected. when i updated to 1.18 and opened it , i recieved a huge amount of lag .
KEEP IN MIND that the lag isnt from the player , rather from the server . In other words you would be running around normally and smoothly and decide to open a chest , you would wait a good 30 seconds for it to register and open . Mobs will attack the position in which you were standing about 20 seconds ago, dropping items teleports them to these places , projectiles are inconsitent ...
you get the idea , the client and the server are basically lagging .
note: - this issue is in single player

• i am not generating new chunks
• i dont know if new worlds or non experimental 1.17 worlds are also facing this problem
• i am playing on ps4
• i definetly had similar issues in 1.17 but they were on a much smaller scale
• i would like to be able to downgrade to 1.17 at will but its impossible.

feel free to let me know if other worlds on ps4 or bedrock generally are facing this problem.