as to the plugin issue, contact plugin developer to resolve your issue, as we do not provide assistance with 3rd party plugins.
in order to uninstall the plugin from the server, you need to delete the folder of the plugin in ow_plugins folder and the record of the plugin in the database in ow_base_plugins table.
However, the plugin may have the widgets, which is why it will leave remains in the components tables, which will cause more issues if you delete it manually. So you better contact plugin developer.