Why when I do a configuration export does the config.tar.gz in tmp not get copied to the sync folder?
The best way to store configuration is to store it outside of Drupal root directory.

For example you will have next project structure:



Where:


config/sync is a directory with your sync configuration.
public_html is a directory with your Drupal 8.


In your setting.php just add this 

$config_directories['sync'] = '../config/sync';


And export your active configuration using drush

drush cex


That's all. In config/sync directory you will a files list of all your configuration.