Here's the continuation of my old SPEED OF SOUND modpack, a lightweight, high-performance modpack made for 1.21.5 with some Quality of Life mods, perfect for Vanilla players that just want performance with shaders :

Blazingly fast loading time
Tons of patches that fix Vanilla bugs
Tons of Quality of Life features, like an integrated shader/texture pack downloader!
Get ready to play with your friends with Essential, who's 100% supported
Everything from Optifine, but 10 times better and optimized (even the stylish grass feature)
Works on every computer, how I know that? Ask my school computer.
Works with only 1 GB of ram, even with shaders! (tested and approved, depends of computers)
Fully multiplayer support and very stable, here be no dragons!
Fully customized, hit & run!

And lot more, try it by yourself !

This modpack requires a minimum of 1 GB of ram, 2 with shaders and I recommend a max of 4 GB of ram if you're not planning on adding other mods.

Here's my school laptop rendering 512 villagers with only 1.2 GB of RAM

SPEED OF SOUND II