Yes.  A SOBR can be a target for a Backup Copy job.

A scale-out backup repository can be used for the following types of jobs and tasks:

• Backup jobs
• Backup copy jobs

You can copy backups that reside in scale-out backup repositories and store backup copies in scale-out backup repositories.

• Veeam backups for Amazon and Microsoft Azure (via backup copy jobs)

• VeeamZIP tasks
• Backup jobs created by Veeam Agent for Linux 2.0 or later
• Backup jobs created by Veeam Agent for Unix 2.0 or later
• Backup jobs created by Veeam Agent for Microsoft Windows 2.0 or later
• Backup jobs created by Veeam Agent for Mac
• NAS backup jobs
• Backup jobs created by Veeam Backup for Nutanix AHV

https://helpcenter.veeam.com/docs/backup/vsphere/backup_repository_sobr.html?ver=120

how about backup copy from SOBR as source to SOBR as target 

Yes, this can be done as well.  See the post above from Cary.

It should be fine, I am using it and I don't see any issues with it.

Yes you can