Below you can see the front view size comparison of Sony A6400 and Samsung NX30. Sony A6400 is clearly the smaller of the two cameras. Its body is 7mm narrower, 29mm shorter and 8mm thinner than Samsung NX30.
Sony A6400 vs Samsung NX30 - Front View 
Sony A6400 vs Samsung NX30 - Top View 
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison