I don't think PhysX should make any difference, although I stand to be corrected on that one....
Those settings aren't obscene, and I would hope that the GTX750 should handle them for most content. What exactly are you testing with at the moment? (Resolution and approximate bitrate if you know them)
If you hit CTRL+J whilst the video is playing, this should bring up the MadVR OSD- Rather than saying the rather unclear 'stutter', this should give you some good stats on what's actually happening
What we need is the dropped and delayed frames figures- You will probably get 10 to 20 here when the video first starts, but they should not be increasing after this.
If they're not increasing, then the problem isn't in the video rendering; This could be all manner of things, so we won't try going there until we've figured out the basics.
-Leezer-