Both Pentax K-1 and Pentax K-1 II have 36.0 MP resolution sensors but Pentax K-1's sensor is Full frame (35.9 x 24 mm ) and Pentax K-1 II's sensor is Full frame (35.9 x 24 mm ).
Since Pentax K-1 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 Pentax K-1.
Another similarity between these two cameras is that both Pentax K-1 II and Pentax K-1 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 K-1 and K-1 Mark II sensor size comparison.
Pentax K-1 and Pentax K-1 II have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.