Both Canon M100 and Pentax K-3 II have 24.0 MP resolution sensors but Canon M100's sensor is APS-C (22.3 x 14.9 mm ) and Pentax K-3 II's sensor is APS-C (23.5 x 15.6 mm ).
Since Pentax K-3 II'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 Canon M100.
Another difference between these two cameras is that Pentax K-3 II'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 M100 and K-3 II sensor size comparison.
As seen above, Pentax K-3 II has a 1.1x Larger sensor area than Canon M100. 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.