Is it possible to link a JIRA project to a Forecast project and then select one of the templates for the Forecast project?
No. If a JIRA project is linked to a Forecast project upon the latter's creation (through the JIRA integration menu and by clicking on the Sync Project option) you will not be able to select a Forecast project template to copy.
In this case, it is better to start creating a Forecast project, use a template, and after the project is created then link it to a JIRA project. To learn more about syncing projects between Forecast and JIRA please visit, Syncing Jira projects to Forecast projects.