Virtuozzo Backup vs. Plesk Backup

[Sellighsphire]

Hello everyone.

I have to manage a website that is managed by the Plesk panel _and_ the infrastructure manager
On the plesk side, a backup script is running, which I can't configure.
It seems that it is backing up the whole server in a xml-file.
It is configured to keep 7 backups.

On the other side, a backup is configured at the infrastructure manager, which
I can't configure either.
It seems to do a full backup and after that a incremental one. After 7 days
it will do another full backup, keeping the old files.

Obviously the server will kill himself, because there will be too many backups that
fill the space. (Backups are stored on the same server/account)

After all, I want to keep one backup job. So here are the questions:

1. which of the backup jobs is better to backup the whole system?
2. how do I stop/terminate/kill/disable the other backup job?
3. how do I configure the remaining one to do a inkremental backup
every day and to do a full backup every 7 days, discarding/deleting
the old backup-files?
(btw.: it seems that the virtuozzo-backup is backing up the old
backup-files, because the files are double-sized every next day :-()

Thanks for your help

Jens