Templates are just definitions that have to be executed in specific workflow transitions. Running a template is possible by adding a special condition/validator/post function to transitions. It doesn't matter how many elements there are in a template, you only need to add one template to execute all underlying elements.
If a template is changed and published, all workflow transitions reflect the change immediately.
Please note that a single template can be used many times, so editing it once can affect many transitions where the template is used. To avoid interrupting user's work when editing a template, we use a publishing technique the same as in Jira workflows. Do not forget to publish your changes.