Unless you are shooting with a video camera there is no reason to render at 23/976 or 29.97. Those fractional frequencies are the legacy -bound nonsense of video cameras and even today there is no real reason to keep those frequencies.. If you were to shoot film you would be bound to, as it should be, integer frame rates. 24fps is your best bet unless you want to target PAL-format markets but even in that case you can convert from 24fps to 25fps.
Shutter speed is the same. If you shoot video then your shutter speed should be, normally, 1/half-frame-speed. So, if you shoot 24fps it's 1/48th of a second or 1/60th ofd a second for 30fps. But be aware that with digital cameras there is no absolute. You can shoot with the shutter at 1/24th for added light or even with the shutter off. They used shutter of with the Sony F23 on the set of "Public Enemies" 
If you're rendering from a 3D package you are not bound to the physics of the shutter unless you want to acheieve a given effect.

Paolo

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