RE: G2 frame rate jumping
That's exactly what my G2 Lite does. You apparently fly out of the range of the program.
On the other topic of FPS, I would think that if the graphics card can keep up with your monitor frame rate at whatever resolution you have selected, there should be no problem. If it's more, it has no effect (other than bragging rights)....if it's less, the on screen video will hesitate, blink, jump, whatever.