Both Pentax K-70 and Nikon D3300 have 24.0 MP resolution sensors but Pentax K-70's sensor is APS-C (23.5 x 15.6 mm ) and Nikon D3300's sensor is APS-C (23.5 x 15.6 mm ).
Since Nikon D3300'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-70.
Another similarity between these two cameras is that both Nikon D3300 and Pentax K-70 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-70 and D3300 sensor size comparison.
Pentax K-70 and Nikon D3300 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.