Have you tried setting the Affinity value to -1 or -2? I believe one or the other disables CPU Affinity to make the game use all available cores.
v1.69 Patch notes:
- Added new option to the nwtoolset.ini file to set the toolset CPU affinity
on multi-core computers. If you have more than one CPU on your PC, then
you can use this setting to make the toolset run on only one of the CPUs
by specifying the number of the CPU (0-31). Setting "CPU Affinity=-1"
will turn off CPU affinity
- The nwnplayer.ini setting for "Client CPU Affinity" now defaults to 0 (a
setting of -1 will be converted to 0). If you need to disable this
feature set the value to -2.
So -2 is the value to use, not -1.
-2 works. Again, when used in conjunction with "Miles 2D Audio", all stuttering is cleared up on my PC. Especially the Bink movies, which was the worst culprit. I still can't get the movies to play from the "Movies" menu (that is, the visuals. The audio track will play, but no video) , though. They'll only play in the normal course of gameplay.