I would say that unless you're dragging around a parachute or similar frontal area then weight plays a far bigger role in how a model flies than drag. Now if you're talking about a racing plane then that's a different story. Then you need to balance weight and drag. But even there weight in the turns needs to be supported and a lighter model in the turns will make less drag than a heavy one turning at the same radius of turn.

On our models the small things like exposed wheels, lack of fillets and other fairly minor items don't mean much. We've got pleanty of power to pull the drag around and it's not like we really care about how many miles to the gallon we get with our models.