This is something I'm running into today with newer PC gamers. There is no system today outside those triple Nvidia Titan and 1080 desktops that deliver steady framerates.

I can't write at length but it's a simple no about steady rates. We can reduce settings to gain more FPS and free up GPU memory and power so when the scene gets busy the frame rate might stay high enough to not get annoying but again no, it will not be steady.

So here I'm telling you this is the current state of PC gaming. I wish you had bumped that GPU to the 960m or higher since well, let's compare.
http://gpuboss.com/gpus/GeForce-GTX-960M-vs-GeForce-GTX-950M shows that some benchmarks are close, some are really hammering the 950m but in games you see a big difference.

If you are stuck with the 950m, then you have to keep reducing settings.