Iris Shaders Mod

If you want to boost your FPS in the game, you should definitely try the Iris shaders mod. What it does is simply doubles your game performance. You will notice a significant increase in FPS compared to that when you played vanilla Minecraft or with the Optifine. Additionally, the mod supports a wide range of popular shader packs, such as Complimentary Shaders or Continuum, so you can enjoy your favourite packs at the same time. Another cool feature I could not skip mentioning is the possibility to switch between shaders with no delay at all. You can even enable or disable the shader pack by just pressing a default K button. 

This mod has high compatibility with other mods, so you will not come across crashes when you plug in your mod. Also to gain a glimpse of more FPS the mod comes with the Sodium mod in it.

Currently the mod is only available for Minecraft versions 1.16.5 and 1.17, but hope soon it will be released for other versions as well.