1) This is not a mod. We're using Curse Forge as another platform for our data pack. If a data pack category is implemented on the website we will convert to it;
2) This pack requires OptiFine. Mob textures and other features simply don't work without it. Make sure to play with OptiFine if you want to install this pack.
"More Mobs" is a data pack that adds 15 new mobs to the game. Currently it's being released in snapshots, and will include 60 total mobs in the full release. At this point in time it adds new spawning rules for mobs depending on structures like Mansions, Mineshafts and Strongholds, underground-specific and biome-specific mobs and random mobs. Everything from a peaceful Wanderer roaming the End to a furious Martyr gliding through the Nether.
If you ever need information about the data pack, visit our official wiki. Also make sure to follow me on Twitter and join my Dicsord for development progress on this pack. You can also subscribe to my YouTube channel where I always upload a showcase for each new version.
Here's a video showcasing all changes in the latest release.