Virtual machines and other vApps can be added to and removed from a vApp.
After you create a vApp, you can populate it with virtual machines or other vApps.
Within a vApp, you can create a new virtual machine, resource pool, or another vApp.
Same you can see below from vSphere Webclient
You can add an object, such as a virtual machine or another vApp, to an existing vApp.
An existing virtual machine or another vApp that is not already contained inside the vApp can be moved into the currently selected vApp.
Configure vApp IP Allocation Policy in the vSphere Web Client
Right-click the vApp in the inventory and select Configuration > Edit Settings
You can edit how IP addresses are allocated for the vApp.
NOTE The deployer typically edits the IP allocation policy and properties. The vApp author typically edits the other, more advanced settings.