What's the most important factor for good webcam image quality?

Reviewers across r/logitech, r/Twitch and r/obs repeatedly stress that lighting beats sensor specs. Multiple threads on the Logitech Brio and C920 note that grainy, flickery footage usually improves dramatically once you add a light, turn off autofocus drift, and set exposure manually. A larger sensor (1/2-inch or bigger) helps in low light, but no webcam fully replaces decent room lighting.