Q: appleid vs supportprofile

I'm nto sure what you mean by "material." In the case of devices, My Support Profile shows the devices that you have added to that site via the Add Products button while the Manage Your Apple ID shows the devices which are currently signed in. Signed in has different definitions depending on the operating system version in use -- see Check your Apple ID device list to see where you're signed in - Apple Support

From your post, one is just that, a profile or list of the devices you have added to your list.  An appleid is nothing more than an account identifier and can be used with a whole host of Apple products and services.  You use your AppleID to create an iTunes and App Store accounts, to create an account here on the forums, to create an iCloud account, an iMessage account, a FaceTime account, etc, etc.  Your AppleID is merely the secure identifier you use to create all of those accounts and access all of those services (or you can create multiple AppleIDs and use different ones for different services).

I Know it's easy to think of your AppleID as an account, but it really is not - it is the identifier and login credentials for many accounts, but the accounts are specific for a given service or product.  You can actually change your AppleID and associated phone numbers, address and so forth if any of those change, but the accounts linked to that ID remain as they were, merely using your new login credentials (i.e. All of your Apple accounts will track with edits you make to an existing AppleID, but will not move to a new AppleID if you create one).