Both Fujifilm X-T20 and Fujifilm X-E3 have 24.0 MP resolution sensors but Fujifilm X-T20's sensor is APS-C (23.6 x 15.6 mm ) and Fujifilm X-E3's sensor is APS-C (23.6 x 15.6 mm ).
Since Fujifilm X-E3's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm X-T20.
Another similarity between these two cameras is that both Fujifilm X-E3 and Fujifilm X-T20 sensors lack anti-alias (Low-Pass) filters. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the X-T20 and X-E3 sensor size comparison.
Fujifilm X-T20 and Fujifilm X-E3 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.