Ricoh GR III has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor . On the other hand, Canon G7 X MIII has a 20.0MP 1-inch (13.2 x 8.8 mm ) sized BSI-CMOS sensor and features DIGIC 8 processor.
Another difference between these two cameras is that Ricoh GR III's sensor lacks 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 moire occurring in certain scenes.
Below you can see the GR III and G7 X MIII sensor size comparison.
As seen above, Ricoh GR III has a 3.2x Larger sensor area than Canon G7 X MIII. 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.