Blending final cut pro 60fps to 30 fps

Your option number 2 would produce exactly the same result you have now.

The choppiness you experience is due to the fact that the shutter speed, while very adequate for 60fps, is too quick for 30fps.

I suggest you do a little test on part of the footage with frame blending and optical flow and see what works best. Processing, especially with optical flow, can take quite a while, so test in a small section before you apply to the whole thing.

Not with that shutter. You might try a third party effect to add motion blur.

Every bit of motion picture footage ever shot produces choppy footage . . . it's just that in most cases our eyes cannot detect it because of persistence of vision.

However, there are certain instances, such as a panning shot over a static subject or something moving across the frame, that will produce an obvious and often unpleasant staccato image.

The motion picture industry recognised this over a century ago and formulated rules for the speeds and angles of motion that could be shot safely.

Your only hope in future, is to be careful when panning static shots and allowing a subject to cross the frame.

Subjects approaching the camera head on are pretty much immune to choppiness as are most diagonal shots.

Of course, the staccato motion of high shutter speeds can be used to good artistic effect to give a feeling of urgency, immediacy and involvement such as is seen in the opening battle scenes of "Saving Private Ryan" and many other action films.