Question about Delock USB Y-cable

Yes, you can. I use it to supply my external audio interface with stable voltage. You could also tape off the corresponding pins on the black connector so that only data comes through there.

Instead of a charger, a power bank also works as a power source via the red plug

This should be possible without any problems. We use several of these cables on various Synology NAS with a USB charger on the red plug and sometimes the same setup on a laptop. The mainboard supplies 5 volts DC as does the USB charger. There would have to be a defect somewhere to damage one of the devices.