This is a big to point out that Drupal is not like wordpress, it doesn't have "premium" plugins, it has modules that are all free to use. It also comes integrated with security and caching in it's core (and as such is a much more robust system).
Drupal does not have a "theme customize" system like wordpress, unless a theme specifically makes one for themselves.. As such perhaps some options such as the Zurb Foundation, or Bootstrap, or the Omega theme system would be satisfactory. In most cases the "customization" happens manually via css and editing page templates, but these have some admin-panel options for look and functionality.
There is no "coming soon" module for drupal, but drupal core has a "maintenance mode" which can be customized (through css/page template coding) to look any way you want.
There are SEO modules, backup modules, and spam protection in the form of captcha type modules, and a very robust contact form module called "webform".
Drupal, while a much more robust and powerful system, relies alot more on manually coding templates and files, as opposed to wordpress's online editing of things.