Having both a standard VGA and a BNC connector will let you attach two machines simultaneously and switch between them. Flicker is a natural by-product of CRT technology. An electron beam paints phosphors with electrons, and the phosphors emit light. So the solution is to use phosphors that don't glow very long, and then to repaint them very quickly. The problem is that there is no fixed rate for a flicker-free display.
Some people are more sensitive to flicker than others.
Also, with the move toward larger screens, more of the monitor's image fills our field of view, so we see more of the screen with our peripheral vision. Whether it was an adaptation to aid in hunting or to avoid becoming dinner ourselves, human eyesight is more sensitive to motion in peripheral vision than in the center of our field of view, so we are more prone to see flicker on larger screens. Flicker tends to disappear when the vertical refresh rate hits between 70 and 75 Hz. The answer is that you may be trading away image quality unnecessarily. To make a black and a white pixel next to each other, the electron beams in the monitor must go from off to on in an incredibly short length of time.