I'm not sure what you mean. For example, if you have two followers, install mod that's add a follower, wonder if you could have three followers then yes, because UFO changes the limit to 15. Unless the follower mod in question changes the number of followers you can get, which is highly unlikely. If you asking if UFO is compatible with most follower mods, then yes. Will they get the features add by UFO, depends on how the follower mod in question is made, if it's a humanoid follower then very likely yes. If you are wondering if UFO will conflict with other mods that modifies followers, then yes, will they work together without glitches/crashes/problems, maybe, maybe not. If you are asking if you can have normal followers (UFO modified) with followers added by mods at the same time, probably yes, unless the mod author did something very wrong.