Qubes has built-in backup and restore for VMs, so yes. Just copy the backup file to another Qubes machine and restore it. However I don't know what you mean by "so only the platform has to be changed underneath." Qubes VMs aren't really intended to be portable to other virtualization platforms (like KVM or VirtualBox), if that's what your asking.
Not sure how template VMs work with Windows guests, but with Linux guests you can keep apps separate from user data, so that you don't have to reinstall apps when you create or delete VMs.
Also, you can install Qubes on a USB flash drive if you just want to try it out.
https://www.qubes-os.org/doc/backup-restore/
https://www.qubes-os.org/doc/windows-template-customization/
https://www.qubes-os.org/doc/installation-guide/#installation-destination