If i get a camera module from which I can read a JPEG image in QVGA resolution, how would you estimate the maximum possible framerate to receive via WiFi?
Connect the camera to the PC. Download a few images. Compute the average size in bytes.
Divide the number of bytes in the image by the baud rate that the two Arduinos are communicating at (which is in bits per second; 10 bits get sent to transfer one byte).
At 115200, 11,502 bytes per second can be sent. If the average picture size is 30000 bytes, it will take nearly 3 seconds to transfer one image.
This all assumes that the camera will dole out the image in small enough parts so that the Arduino does not need to store the hole image.
Typical video has a frame rate between 15 and 30 frames per second. At 1/3 of a frame per second, your video will be very choppy.