Here are some comparisons to get you started:
Nikon Z 6 compared to Nikon Z 7
Nikon Z 6 compared to Nikon Z 7 (both overexposed 2 stops)
Nikon Z 6 compared to Nikon Z 7 (both underexposed 3 stops)
Nikon Z 6 compared to Canon EOS R
Nikon Z 6 compared to Sony a7 III
Note that these images were processed in their respective brand's RAW converter (Sony-blessed Capture One Express for Sony was used for the a7 III results). With a sharpness setting of 1 (our current Nikon and Canon standard), the Canon appears under-sharpened. Note that I'm sharing ISO 50 results for this camera.