Iris VS phosphor-fabric

Iris Shaders + Sodium - Link - Indium - Link - (Indium is needed for many other Sodium based FPS increasing mods) - Increases performance and shaders performance

You can install iris from here: https://irisshaders.dev/download and they have a complete installation guide here: https://github.com/IrisShaders/Iris/blob/37f491553cea26241a8561da90917c740d7a573c/docs/guide.md

Downloading the latest version off of the official Iris website or GitHub should be safe: https://github.com/IrisShaders/Iris/releases

Phosphor (another optimization mod by the Sodium devs, targeting the built-in lighting system)

Sodium Phosphor Lithium also get iris but I don't have download link

There’s lots of lightweight shader packs designed for low-end PCs. For an optimized, smooth shader experience I’d recommend installing Fabric, Sodium, Lithium, Phosphor, and Iris Shaders.

I would suggest you to use Sodium or Iris - Overall Performance Improvement / Iris If You Wanna Use Shaders Too Lithium - Improve CPU Usage LazyDFU - Launch Game Faster Phosphor - Improve Light Engine Hydrogen - Reduce Memory Usage

Low performance is to be expected with your config. You can try to install these performance mods for minecraft : * Iris that contains Sodium * Sodium, don't use it with iris, it already has sodium. * Lithium * Phosphor

Lithium is only for Fabric. There's also Phosphor to improve lighting performance.

You can get better performance and retain vanilla features by using Fabric with phosphor and lithium.

for newer versions Sodium+Lithium+Phosphor (+aditionally hydrogen)

Please use the Randon World Format for it uses less RAM and uses less file space and please use the Lithium Lighting Engine for the same reason.