Regarding the 520:
It emulates the Amiga 600‘s internal IDE. As weird as it sounds - this device is called „scsi.device“.
To use it in an otherwise unexpanded A1000, you need to create a boot disk with an altered KickROM disk. You need to put this scsi.device from the a600 into the KickROM that is loaded from disk. This is possible but I don’t know how.
You might be better off with a Kickstart-replacement for the A1000, such as the one discussed here in the forum:
Then you can boot from the 520 without any disk.
You might want to consider to open up a new thread for this as this can be easily overlooked in an existing discussion regarding a ZIP drive