so....

it sounds like (and correct me if i'm wrong)  you're talking about a scene with people and fairly simple surroundings.  as opposed to (for instance) a still life, a portrait, an arch. vis., etc.  for instance, i've seen caustics in most arch. vis. (lots of wine glasses, vases, etc.) and a lot of still lives.   colored shadows are rarer, but not so much. put wine in those glasses or colored glass in the room and you should have colored shadows.

lots of those special effects are common in real life.  so if you're cutting out those elements (which is cool), could you explain exactly what part of  (or type of) "realism" you're trying to test? (realism quoted because it's definition can be so broad and subjective)

again, i suggest having a photo as a control.  because while you should definitely be able to optimize materials, i think it would be kind of disingenuous to switch from one type of material to another.  that is, if something is bronze, everyone should be doing bronze, and if something is stone tile, everyone should be doing stone tile.

V4 would be more problematic than some other figure.  with a non-DAZ figure you could actually share a .cr2 file among Carrara, Vue, Poser and D|S that would reference all the necessary pieces.   also, if what you're testing is mainly light and not, for instance, skin shaders, textures or even modeling, it might be better not to have a human figure at all.