Clarity on Drupal caching? Drupal 8 uses Opcache, while most people still use APC for Drupal 7. I am not sure which of the two to use for a Drupal 7 site, because it appears there is no Opcache module for Drupal 7. There is this: https://www.drupal.org/project/opcache, but I don't think that will do the trick as it is a dev module.

Which of the two options should be used for Drupal 7? And if you choose Opcache, please suggest the best way to implement it, seeing as the module is in dev mode? Assuming I am using PHP 5.5 (i.e. a version that supports OpCache, which means it would be my preference as well).
Drupal 8 recommend using Zend OpCache (a PHP extension), which is enabled at server side, and it caches PHP code; it is not used for caching data.
For data caching, Drupal 8 automatically uses APCu without requiring third-party modules, if the PHP extension is enabled. See Several cache bins now use APCu caching by default, which states:


  In order to improve cache performance, Drupal 8 now has:
  
  
  A cache.backend.apcu service that site administrators can assign as the backend of a cache bin via $settings['cache'] in settings.php for sites running on a single server, with a PHP installation that has APCu enabled, and that do not use Drush or other command line scripts.
  A cache.backend.chainedfast service that combines APCu availability detection, APCu front caching, and cross-server/cross-process consistency management via chaining to a secondary backend (either the database or whatever is configured for $settings['cache']['default']).
  A default_backend service tag (the value of which can be set to a backend service name, such as cache.backend.chainedfast) that module developers can assign to cache bin services to identify bins that are good candidates for specialized cache backends.
  The above tag assigned to the cache.bootstrap, cache.config, and cache.discovery bin services.
  
  
  This means that by default (on a site with nothing set for $settings['cache'] in settings.php), the bootstrap, config, and discovery cache bins automatically benefit from APCu caching if APCu is available, and this is compatible with Drush usage (e.g., Drush can be used to clear caches and the web process receives that cache clear) and multi-server deployments.


So, if you are using APCu as data cache on Drupal 7 (which require installing a third-party module), keep using it; when you will port the site to Drupal 8, you will not need anymore a third-party module, to use APCu to cache data. That is why the APC - Alternative PHP Cache module doesn't have a Drupal 8 version.

The module you are linking just allows Drupal to report status information about the cache and reset the cache; it is not a module you need to use Zend OpCache with Drupal.