As highlights, Nice Mop includes:
Create | Vanilla+ mechanisms, based around gears and kinetic energy
Origins | Races with pros and cons. (for some reason, Phantom Origins seem to suffocate in blocks.)
Deeper and Darker | Adds a new dimension themed around the Deep Dark. (Removed after version 2.0)
Artifacts | Adds Terraria-like equipment to the game.
Easy Villagers | Makes villagers easier to deal with
Farmer's Delight | Adds more crops and foods to the game.
Spice of Life (Carrot Edition) | Rewards players for a variety of foods.
Biomes O' Plenty | Adds way more biomes and blocks
MopCards | A Trading Card game for use with other players (Added after Version 2.5)
The name comes from a very stupid mistake.
It also comes with my custom "Better Shrieking" datapack, and the "Minimal Armor" datapack I found.
(Better Shrieking makes Sculk Shriekers less scary, Minimal Armor makes vanilla armors less intrusive, so you can see people's skins better.)