Panasonic G85 has a 16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Panasonic GH5 has a 20.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine processor.
Another similarity between these two cameras is that both Panasonic GH5 and Panasonic G85 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 G85 and GH5 sensor size comparison.
Panasonic G85 and Panasonic GH5 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Panasonic G85 has 27% larger pixel area compared to Panasonic GH5, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Panasonic G85 and Panasonic GH5 sensors have been tested by DxO and the results show that GH5 has a better overall score of 77, 6 points higher compared to G85's score of 71.