Below you can see the front-view size comparison of the Fujifilm GFX 50S and Fujifilm GFX 50R. The Fujifilm GFX 50S is 13 mm narrower and 3 mm shorter than the Fujifilm GFX 50R but it is also 25 mm thicker.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.