If you uninstall content in the TSR CC manager that still shows in your game even though it is no longer in CC Manager, you have a second copy of the file installed - probably loose in your Mods folder somewhere.
If you uninstall content in the TSR CC Manager but it reappears shortly after in the CC Manager and your game, the culprit is most likely Onedrive putting it all back again from your cloud backup (other backup tools might do the same).
While we strongly advise that you pause Onedrive's syncing while you install content, when uninstalling, leave Onedrive running so that it can see the content being removed. Alternatively, stop Onedrive backing up and restoring your Documents folder - see Onedrive for more information on how.