Unfortunately, frame rate limiting in NVCP doesn’t work if you have the game using multiple monitors. Instead, it divides up the frame rate number between the monitors. The sim vsync doesn’t have that issue.
To be honest, the difference between 30FPS and 60FPS doesn’t matter to me. Not saying I can’t see the difference - I can - but 30FPS is fine for my old eyes, as long as it’s smooth. So I’m not terribly fussed about frame-gen.