The iCloud drive is a good way to share small amounts of data across several different devices, but the amount of space you get for free is limited to 5GB, which is not that much, and you must subscribe to expand the amount of data if you need more for monthly fee, which might be a good option for some folks who use this service.
https://support.apple.com/en-us/HT201104
If you are buying a new Mac and just want to migrate things from the old Mac, you could try directly connecting the two Macs and using Target Disc Mode on the old Mac, then using Migration Assistant to copy files from the old Mac to the new Mac.
https://support.apple.com/en-us/HT201462
For any computer, new or old, you should consider getting an external hard drive to maintain a backup of the internal hard drive. I like to use Carbon Copy Cloner, since it can run scheduled incremental backups and keep your back up current.
https://bombich.com/
If your data is really important, get two hard drives and make two backups, use one drive for Time Machine backups, and one for Carbon Copy Cloner backups. Time Machine can easily recover past versions of individual files when you need it, but if your hard drive crashes you can reboot immediately from the Carbon Copy Cloner bootable clone drive and finish that important project you were working hard on to meet that deadline, and restore your data to a new hard drive at your convenience.
It never seems worth the effort until the day when your hard drive fails and all of your data is gone. I hope this info helps, and gives you some options to consider. Have fun with your new Mac!
