Below you can see the front-view size comparison of the Fujifilm X-T30 and Olympus E-M5 III. The Fujifilm X-T30 is clearly the smaller of the two cameras. Its body is 7mm narrower, 2 mm shorter and 3 mm thinner than the Olympus E-M5 III.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.