Below you can see the front-view size comparison of the Olympus E-M10 II and Fujifilm X-A3. The Fujifilm X-A3 is clearly the smaller of the two cameras. Its body is 3 mm narrower, 16 mm shorter and 7 mm thinner than the Olympus E-M10 II.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.