A VApp template allows you to quickly deploy the required number of virtual machines in a single action. If you need to frequently create identical groups of virtual machines (vApp), then create a template on the basis of this vApp.
For this action it is not necessary to stop the vApp. But if you want to make changes to the virtual machines contained in the vApp in the process of creating a template, then the vApp must be stopped.
Important: You can not make any changes to the original vApp and the virtual machines inside it until the action is complete.