Does the first part of the new Backup and Sync App from Google simply
backup "My Computer" or "My Laptop"? And only the second part of the
settings "Google Drive" can sync between devices?
The first part just let you specify which folders on your local device you want to be backed up to cloud. Its just its name is "My Computer"; if you are using it on a laptop, it refer to your laptop. The second part enables you to choose which items from the cloud to sync back to local device (your laptop).
It would be nice, if one could sync the backup folders. Example
Google Drive Folder: D:/Google Drive
Also synced Folder: C:/some_folder
From Testing I can still only sync contents within Google Drive. "My
Computer" is simply backed up to the cloud, which is a shame.
"D:/Google Drive" is the source to be backed up to cloud and it can also be local location storing the files sync from cloud; "C:/some_folder" can be the source to be backed up to cloud too. "My Computer" tab in Google Drive is just a tab used for saving files backed up from local.
Tip: Usually, files from local to cloud, Backup and Sync calls it "backup"; files from cloud to local, Backup and Sync calls it "sync".(personal understanding)
Moreover, how would I restore the backup folders on my machine if I
had to reset the machine?
If you reset your machine, reinstall Backup and Sync and reestablish the backup and sync service, files in "My Computer" tab in Google Drive will be automatically restored (synced) to your local storage.