Thanks for the rod recommendation.

Anyone use the helical coupler to fix the z wobble?

Would not really fix z-wobble, unless you have some weird z-wobble. can introduce vertical slop. Also multiple people have used it, worth looking around.

M3 is often used instead of M5. An M3 rod will flex which allowes some angular misallignment, like a helical coupling.  M3 will also have a finer pitch, and hide layer height errors with finer resolution.