You can identify the mono plugins by their filepath, which is displayed near the bottom of the window in Plugin Manager when you click on any plugin. Then if you click on the Plugin Properties button it allows you to rename the plugin. I use to add the text "(m)" to all the mono UAD plugins. Nowadays I don't use the mono ones as I have had issues with some of them.
You can remove them by deleting the DLL files in Windows Explorer. I have deleted all the UAD plugins that I do not have licences for. This is mainly because it's distracting and annoying to have a long list of items that you can't use. But it's also tempting when it's too easy to enable one of them and end up making a purchase. But I keep a backup of the files just in case I change my mind.