For the sake of brevity, I will only speak on A Better ADVENT so that you can get a grasp of what the mods by creator DerBK have to offer and decide if you would like to check those out as well.
The other two mods related are A Better Barracks and A Better Campaign. Part of a collection of mods that overhaul major aspects of the game, A Better ADVENT (ABA) is a mod primarily concerned with adding an extra challenge to the game by introducing increased enemy variety as well as improved AI and improved enemy types.
