2 things in one unit is two things, and the two things “enable”. Is it more common in American speech for people to follow the singular word, so far away from printers, with “enable”?

I would say that “printers.. each enable” both is right and sounds right.

From the user’s point of view, not the mechanic’s, is your unit essentially all one device, such as something that prints everything out the same port? This will tell you if it is a singular

or plural.