If you want to optimize the PHP Opcache on Plesk, here are the config files:

/opt/plesk/php/5.6/etc/php.d/10-opcache.ini
/opt/plesk/php/7.0/etc/php.d/10-opcache.ini
/opt/plesk/php/7.1/etc/php.d/10-opcache.ini

http://php.net/manual/en/opcache.configuration.php

In your scripts you can use these commands to invalidate files.
opcache_reset()
opcache_invalidate($file, true)