Update:
Did a TestBackup of one DAG-Node, currently around 1.2TB.
Backup to local Null wrote 830MB/s
To Null on another Node (connected via 20Gbit LAN) it dropped to 450MB/s
to actual Drives it wasn't that much a drop but still noticable
Average of 210MB/s direct versus 170MB/s when adding the Network-Link.
Any recommendation is very welcome.