Let's say you subscribe to the basic plan, install 10 apps and then unsubscribe. As I understand it your app will continue to run, you just loose update and management abilities linked to the Cloudron sub right ?
As you said, you wont get further updates to the apps, however everything will continue to run as is. Also you will be able to further manage the server or reconfigure already installed apps. Other features like automatic backups will also keep working.