Hello Punk,
Welcome to the Apple Support Communities! We see that you have a questions about how iCloud Documents works with your Mac files.
Since you have uploaded the desktop and documents to iCloud, you will be able to access them from any device you can access the iCloud website. This article will give you the additional details under "Access your Desktop & Documents files on another device," in this article: Add your Desktop and Documents files to iCloud Drive.
This means that if your old Mac were to become inoperable you will indeed be able to access everything that is in iCloud.
All the best.