As far as UI mods go, they do share the same DIRECTORY; they do NOT however, share the same setting of WHICH UIs are on per-ACCOUNT. I have Omen, recap, CTRA, and a few misc mods disabled on my alts, and all of the above enabled on my lead. The little "Addons" button at the bottomleft is your friend, and saves "Which UI is on and which are off" to a Folder in your wow dir named for EACH account; if you enable or disable for one, it's not changed for the other. Never has, either, I've still got my beta Account name's folders in my dirs lol