Drop in picture quality as an effect of resistance varies depending upon the size and material construction of the signal conductor. Most video cables use conductors that are made from copper, tinned copper, or silver plated copper. With this in mind, the only variable left is the size of that conductor ... the larger the conductor is, the less resistance it presents to the signal over long runs.
As an example, our X-60, at a run of 25 feet might introduce some slight loss because the conductor presents an overall resistance of around 1.7 Ohms at 25 feet (at 20 degrees Centigrade).
Digital video is another issue, and length is not of the same concern.
As for delay and synchronizing picture with audio, the video signals travel at nearly the speed of light - there would be no perceptible delay between picture and sound.
