Make no mistake, you've been very helpful; I'm grateful.
If I understand you're cautionary note there, it sounds as if the rabbit hole maybe goes deeper than I first realized. Initially I made the (unconscious) assumption that the pre-built SDL2 libs I grabbed were built with mingw/g++...but in reality I think it's more likely they were built with VS. Now I realize I've made the same assumption about mingw-w64 itself. @_@ Possibly it too was built with VS (to function easily in Windows) which may further stymie my efforts here.
Whew, haha.