Both Leica M8.2 and Leica M8 have APS-H sized 10.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another similarity between these two cameras is that both Leica M8 and Leica M8.2 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 M8.2 and M8 sensor size comparison.
Leica M8.2 and Leica M8 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.