Where does webcam money stop buying picture - is anything above about a hundred doing something?

Resolution is the least important number on the box and it is the only one they print in large type. What changes as you go up in price is sensor size and lens aperture, which together decide how you look in a room that is not brightly lit, plus autofocus that does not hunt every time you move, plus less aggressive sharpening and noise reduction baked into the image. The steepest part of that curve is in the low hundreds and it flattens quickly after. Also, unglamorously: a light in front of you will change your picture more than any upgrade in this price range, because every camera looks good with enough light on the subject.

Roughly how the bands played out for me across four cameras. The cheapest tier is a small sensor with fixed focus and heavy processing - fine in daylight, mushy in the evening. The middle tier is where autofocus and low light get usable and where I would stop for meetings. The top tier mostly buys you field of view options, better glass and firmware that does not oversharpen, which shows up in recordings and is invisible on a compressed call.

One window, one lamp: put the lamp behind the camera pointing at your face, bounced off a wall if it is harsh. Then decide whether you still need a new camera.

Pushing back on resolution barely matters. It matters for exactly your second use case: recorded demos, where you may want to crop, reframe, or deliver at a higher resolution than the call would ever carry. For the calls, the top answer is right and 1080p is plenty. Buy for the demos, since that is the harder requirement and it costs little extra.

I bought a 4K unit, ran it at 1080p for a year because that is all the conferencing app would send anyway, and could not tell the difference in a blind comparison with a colleague's cheaper camera. The money was wasted for calls. It was not wasted for the demo recordings, where I crop in and the extra pixels are actually doing something.