I've only ever encountered 2 problems when it came to nVidia and SFC gameplay.
The first was when I was still running on my old RIVA TNT 2 Ultra AGP card, and when I had the most updated drivers for the card installed, and was playing SFC3, the cursor would disappear from sight when I would move it down to the lower half of the screen, yet when I used the original card drivers, I didn't have that problem. But gameplay was even worse. The card was very old by the time I got into SFC gaming, so I knew it was the card giving me problems.
The other occured on both my old RIVA and on my FX 5200 card. Sometimes the graphics would go all wonky and the colors would turn pyschedelic. In the least extreme of the cases, my ship would still appear normal, but everything else, including ships, would be nearly impossible to identify by sight. I had to rely on the HUD in the corner of my screen and on my UI to determine what shield front that was facing the current target. And in the most extreme cases, my ship wasn't even visible. Everything looked like a light show of different colors. And restarting from a cold boot wouldn't fix it every time.
Don't have either problem anymore.