Performance
If you're looking for ways to improve Minecraft's performance, these are the main Mods to use:
Sodium
Sodium is capable of improving performance significantly. It also fixes several other graphical issues and provides some useful features.
Embeddium
Modern, Vintage, Archaic Fix
ModernFix implements numerous bug fixes and optimizations for Minecraft 1.16 and newer.
VintageFix and ArchaicFix do similar fixes for 1.12.2 and 1.7.10 respectively.
Saturn
Saturn optimizes Minecraft's RAM memory usage.
Lithium
Lithium optimizes a bunch of Minecraft systems such as Physics, Mob AI, Ticking, and more.
Lithium is primarily available on Fabric, but has Neo Forge versions for 1.21.1 and newer.
For older versions there is a LexForge fork called Canary for 1.18.2 - 1.20.4.
Krypton
Krypton optimizes network handlers, lowers tick times on Servers, and has several other optimizations.
Krypton is for Fabric only, however there is a LexForge fork for 1.18.2 - 1.19.3 called Pluto.
Other
There are of course many more performance Mods available, have a quick browse for what you want:
curseforge.com
modrinth.com
Additional performance topics:
Java Arguments