While installing mods manually, it’s better to keep a track of all the packages within. So in case you want to remove a mod, you can easily cherry-pick the mod-specific files and remove them. Being said that such a process is a risky affair and can even corrupt your game. The best bet is to uninstall Skyrim and reinstall it. It will roll back your changes and remove all mods. Alternatively, you can use Vortex Mod Manager to track all the installed mods and remove them as you feel. This is by far the easiest way to safely remove mods.