CPU Usage is very high and low fps

So i found out that 1.16 pre 3 & 4 is using excessive amount of CPU. And my fps drops to like 20 fps where i usually get between 80 - 100 

 

I tend to play at around 20 % Cpu Usage. 

 

There is 2 images.
mc.png is 1.16. Pre 4
mc 2.png is Optifine 1.15.2 pre 23