> Utilizing any 12V-capable
If so, this is usually at a VERY low wattage. they usually go to a max of 2.5 or 3A max at 12V. I would expect it would use 20V and step-down as 20V is more generally available at a high Amperage. (Note: 3A is the max possible for cables without an E-marker, os if often regarded as a ceiling). This would have made the device much bigger (and more versatile. a clear trade-off).
Actually, I am more concerned about -12V, ... at 0.1A. That seems rather low. Also, the 12V rail itself is only 1.0A. The original supply did 12V@2A and -12V@0.5A if not mistaken, and so does the C64psu.com. Overall, rather low Amp values. This might affect 'stability' if your machine is expanded (although it claims: "of even the most expanded configurations"). Curious if they can share some details. I have a BlizzardPPC in my A1200.
> allows users to tap into a vast array of affordable and readily available “power bricks”
if DC5521 at >12V to 20V is possible, that would be great, as this allows you to use a Lenovo or generic laptop brick, or a USB-C trigger cable. Perhaps something I should make ...