In vanilla Skyrim, all of the followers are much the same. They play the same, and feel the same – they don’t feel unique. The purpose of Yagisan’s Expanded Skyrim – Companions is to try and make each companion special in their own way, so you have a reason to take them. Their names, background story, and in game events will be taken into account, along with Yagisan’s vision for each companion, and the end result should be a more diverse set of companions.
Please ensure you have all required mods listed in dependencies installed or you will crash to desktop on startup.