You don't image it. You drag and drop ISOs into a directory on the SSD, and the USB device emulates a DVD ROM drive with the contents. You choose the ISO through a small screen and button on the device.
not the OP but I use the IODD ST400 for this purpose and wish I had gotten something like this long ago
Way too many unnecessary features and too expensive. The 2531 is perfect.
I've had this since about 2014.
I think both of them have been at the same price for at least 2 years now.
All things being equal, simple and proven is better than over-complicated and extraneous.
Can confirm, also have 2 IODD devices for this purpose, though I usually grab my (simplest) USB stick that has netboot.xyz flashed to it, and just boot off that, and select whatever netboot image I want and have it get everything from the interwebs. No need to ever update this workflow.
Will netboot.xyz boot from a WiFi connection? I've always assumed no, and most of my machines do not have Ethernet jacks anymore.