Maybe this also contains some suggestions, but this is a serious problem.
The screenshots "proof", that this is
- Not a problem with the intergrated server, this handels the entities fine
- The problem is with the client, and more with the rendering
The main problem is that the fireball has too many particles...
I will also post this as a suggestion in the reddit suggestion, but as it is a so heavy problem, I guess you can even count it as a bug.
- Fireball: 17 FPS; 144 Count; Lag:No
- WitherSkull: 71 FPS; 1016 Count; Lag: minimal
- Arrow: 37 FPS; 764 Count; Lag: minimal
Lag relates to the "Timer" score on the side which is a fill clock counting from 1000 til 1020 in 1 second (+1 every tick)