The trick to great picture quality is to use good lighting and drop the ISO on the video as low as possible. I've been using Reincubate Camo for my iPhone along with Key Light Air Lights. The quality is better than any webcam. Most webcams crank up ISO so they can work in the dark and that is what ruins picture quality.
This cannot be overstated. While I agree with many of the camera recommendations in this thread the most important factor is enough light.
Even the worst webcams go from absolutely trash to something usable if you add better lighting to you subject.
And when people start thinking over lighting you can move away from your window so you do not have that as a powerful backlight. Look out the window and the webcam will have much better results.
Given my limited understanding of photography that is not really possible with small sensor sizes. Phones can achieve that using computational photography, but I don't think it's possible using optics on webcams.
Yes, optical depth-of-field is only possible with reasonably big sensor sizes and wide-open lens.
Reportedly, Huawei P40 Pro has an IMX700 sensor with the 1/1.33" diagonal. I didn't run the numbers for it, but it is big enough that with a bright lens it will produce bokeh.
