Do you mean the ones that are sold as drive duplicators? Those were the most affordable per HD of what I found. I don’t really want to have a button that would erase or write over my drive though. That’s asking for trouble. A couple of reviews I read mentioned that the particular devices were really aggressive about power management, and would turn themselves off after 10s or 30s idle. Which sounds very annoying but makes sense if the main thing is to clone drive-to-drive. Not sure if they’re all like that.

never do anything port-powered when connecting drives over usb

Anything? Some of my “portable” type HDDs don’t have external power input. So there must be some situations in which it is feasible?