how to uninstall a plugin when there is no cp option
It isn't possible to uninstall a disabled plugin; you'll need to first enable the plugin, and then the Uninstall option will be available.

The correct way to remove a plugin is actually to first Uninstall it. After uninstalling, you can either run composer remove vendor/plugin-handle from the command line, or select the "Remove" option from the Control Panel (the "Remove" option is available for any plugin that isn't currently installed).

If you do it the other way around – i.e. remove the files before uninstalling the plugin – you're probably going to see some issues.