All of the titans have individual stats and unique abilities, including crystal hardening for the Attack, climbing walls and ceilings as the Jaw, and emitting deadly steam for the Colossal!
The pack includes configurable Titan Stealing and Stacking functionality!
You can read more about the pack on the wiki.
As you can see above, the Jaw has four forms - Porco's, Marcel's, Ymir's, and Falco's
The Attack can crystalize, the Female can harden, and the Colossal can nuke! 
Unlike almost every other Titan Shifter origin, titans that should be posed differently actually are. 
The Warhammer Titan has a special set of hardened weapons it can generate on the fly. 
Warhammer pose from BetterCombat
Additionally, the Cart Titan can equip different mounts to gain either saddles, barrels, or an anti-titan rifle. 
You can craft injections to store spinal fluid from titans. You can then inject that spinal fluid into any mob or player to turn it into a mindless pure titan. There are nine different pure titan skins, and their sizes and stats are randomized - although the latter can be influenced by using spinal fluid from specific titans. 
Skin credits (also included in datapack)
Some screenshots taken with Solas Shader
