Most of the Jira integration capabilities are similar if you use Jira Software or Jira Core. The main difference is the issue types and how you map Aha! Features and Requirements.
Tasks and sub-tasks
This is the recommended configuration if using default issue types in Jira Core.
Requirements will be created as sub-tasks of task issue type linked to the parent feature.
If using integrations 2.0 for Jira, you have the option to map tasks to Master features. This is most appropriate when sub-tasks in Jira are larger, more descriptive work items, and tasks themselves take multiple releases to be complete.
Features will be created as sub-tasks of task issue type linked to the parent Master feature.