Ricoh WG-6 has a
20.0MP (1/2. ) sized BSI-CMOS sensor . On the other hand, Fujifilm X-E3 has a
24.0MP APS-C (23.6 x 15.6 mm ) sized CMOS X-TRANS III sensor and features EXR Processor III processor.
One other difference between these two cameras that is worth mentioning is that Fujifilm X-E3's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the WG-6 and X-E3 sensor size comparison.
As seen above, Fujifilm X-E3 has a infx Larger sensor area than Ricoh WG-6. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.