Proper term for 2/3-bolt compatible shoes
I'm not aware of a widely accepted term for multi-compatible shoes. Different manufacturers and retailers will probably each have their own way of referring to them. Not all retailers list that a shoe handles both, or even show a picture of the sole, which is frustrating.

FWIW, in my experience, shoes that handle both 2-bolt and 3-bolt cleats tend to be more at the low end; you won't find a lot of options at the high end, where paper-thin carbon soles and weight minimization militate against putting extra holes and two sets of backplates in.