Here are some images from some test shots from today, made in an attempt to get a feel for the extent of noise reduction resulting from shooting in Pixel Shift mode.
Images shot with Pentax K-3 II
First shot (3870) f3.5, 1/13s, ISO 200
Second shot (3871) f3.5, 1/50s, ISO 800
Third shot (PS_normal_out) f3.5, 1/50s, ISO 800
I have selected a small portion of the shot that best visually shows differences in image quality due to noise, and taken a screen shot of all three images at pretty much the same magnification. The above images are in order left to right.
Not the most scientific process, but might help.