vanillatweaks.net includes many small non-breaking modifications to the game, such as resource packs that subtly change block/item textures.

Fabric is a Minecraft mod loader/toolchain that allows other plugins to be added to your client:

• Krypton improves Minecraft's networking performance and uses the system zlib on Linux
• Sodium is a replacement rendering engine focused strictly on performance.
• LambDynamicLights adds various dynamic lighting effects.
• Enhanced Block Entities replaces block entities (such as chests) with static block models to improve performance
  • caveat: the chest open/close animation flickers a bit when swapping models
• Ok Zoomer adds an optifine-like zoom key
• Camera Utilities allows more specific camera repositioning, detaching, and other features.
• ShulkerBoxTooltip provides a preview of shulker box contents when viewing them in the inventory.