The reason why scaling dropshadows were used in older games like Mario 64 was because it adds a measure of how far away the player is from the ground. Since realtime shadows were not possible back then, it was a good trick. With a realtime reflection, you don't need that trick anymore, because the reflection is a more sophisticated cue to the player to measure distance between ground and the object itself. I think this might be tested through trial and error; I suggest to fade out the drop shadow on realtime-reflective surfaces.

Faintness in reflections are especially dependent by the distance of the reflected object to the surface, otherwise it looks dull. I made a quick mockup with a 50% reflection-surface. In the left you see a perfect reflection in the right a fainted one; please take a look at the cube near the plane and how the reflection gets blurred the farther the cube is away from the surface:



To achieve a fainted reflection in realtime games, you could use a high- or mid-res RT and do the blurring in a postprocessing step. If you write the depth of the render view of the mirror image into a seperate screen-space render target, you can use this as a cue for a dynamic blur shader, so that you get the depth-fainting of objects far away from the mirror surface.