composer show project/name
Example: composer show drush/drush
This will show version numbers, source (repo), dependencies, etc.
Below quoted from https://pantheon.io/blog/avoiding-dependency-hell-site-local-drush
If you have already tried your hand at using Composer to add Drush to your Drupal 8 site, you may have noticed that your site-local Drush was placed in the vendor/bin directory inside of your Drupal root. You may be wondering whether you should put this directory in your $PATH, or what you should do if you have more than one Drupal 8 site on the same computer. Fortunately, Drush has already anticipated this problem for you and solved it. All that you need to do is update your global Drush—the one that is on your $PATH--to Drush 8.0.0-rc1 or later. Then, any time you run a Drush command, the global Drush will notice that there is a site-local Drush, and will use it instead.