These mods greatly effect gameplay of Minecraft

• Create Mod: engineering and technology
• Better Combat + Simply Swords: Combat and Weapon overhaul
• YUNG's Mods: overhaul of vanilla structures
• Tectonic: overhaul of world generation
• Decorative Blocks, Supplementaries: adds many different building blocks to the game
• Fabric Seasons: adds seasons to the game
• You're in Grave Danger: adds gravestones to the game when you die, saving your items
• Farmer's Delight Refabricated: adds many new crops and foods to the game
• Inmis: adds backpacks to the game

These mods just make some small QoL changes to the game

• AdditionZ, VanillaRefresh, VanillaTweaks: all of these mods make miscellaneous additions to the game
• AmbientSounds and Auditory Continued: adds misc sounds into the game
• Artifacts: adds artifacts to the game that give the user unique abilities, and can only be found in loot chests
• Trinkets: works with Create, Artifacts, and Inmis to provide extra inventory slots for those items
• Banner Flags, More Banner Features: adds more uses for banners
• AudioPlayer: allows for the creation of custom music discs
• BlossomHomes, adds a /home command, configurable by server
• Botany Pots, adds pots that you can grow crops in
• Carry On, carry mobs, players, and chests
• Comforts, adds sleeping bags, hammocks and other changes to sleeping in Minecraft
• Easy Anvils, Easy Magic: respectively changes how anvils and enchanting tables work
• Ender Dragon Fight Remastered: Overhauls the Ender Dragon fight
• Elytra Slot: adds a slot to Trinkets for Elytra
• Figura: allows players to create custom BlockBench models to use as skins
• Lootr: makes player specific loot chests, so even if someone loots something before you, you still get loot
• More Mob Variants: adds variants of mobs
• Not Enough Animations, Eating Animation: Adds misc animations to the game that should be in vanilla
• Smarter Farmers: farming villagers replant crops
• Simple Voice Chat: adds voice chat