I have two webcams, which are mounted close together. I plan to use them to find out the true depth of certain pixels of images. Suppose I use a standard multi camera calibration setup and find out the relative orientation of one with respect to the other camera, can it perform as well as a stereo camera setup for depth estimation? What are the challenges typically? How accurate must the calibration be?
The challenges you are going to face is more how to mount the cameras and find the relative positions between them (also the rotation). You can find a lot of designs for mounts for the cameras, also 3D printers' designs. The calibration is pretty similar to the one for one camera chess pattern etc. There are also a lot of tutorials explaining how you should proceed. Have fun!