Canon G9 X II has a
20.0MP 1″ (13.2 x 8.8 mm ) sized BSI-CMOS sensor and features DIGIC 7 processor. 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 G9 X II and X-E3 sensor size comparison.
As seen above, Fujifilm X-E3 has a 3.2x Larger sensor area than Canon G9 X II. 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.