Configuration management is great. But you'll encounter some difficulties at first when importing existing config to a new site. A typical error is the "Entities exist of type" error. Here's how to fix them.
The reason is that the standard installation profile installs some entities (f.e. from the shortcut module). You'll need to delete them first before the error goes away. To fix these programmatically:
drush ev '\Drupal::entityManager()->getStorage("shortcut_set")->load("default")->delete();'