iCloud

Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.

It is possible to sync data from a Mac to iCloud if you turn on those options (e.g., iCloud Photos, iCloud Drive including the Desktop & Documents option). Syncing has some of the benefits of a backup (and the benefit of being offsite) but is not the same as a backup. Major differences include the fact that not everything on your Mac can be synced and the fact that if you delete something, accidentally or otherwise, there is only a limited time period (30 days in most cases) during which it can be recovered.

Also see: How to back up your Mac - Official Apple Support

And more information on syncing in:

Set up and use iCloud Photos - Apple Support

and

Access and manage your files in iCloud Drive - Apple Support

and

Add your Desktop and Documents files to iCloud Drive - Apple Support

Yes, there is. The Photos app syncs via iCloud Photos so there is no need to sync the Pictures folder. I'm not knowledgeable about syncing music but it does have it's own mechanism as well.

See: Set up and use iCloud Photos - Apple Support

Either that or create new folders for those things in your Documents folder (if you have Desktop & Documents iCloud option on) or in your iCloud Drive folder if you don't have Desktop & Documents on.