Depends how Anal you want to get.!!! . . . Really with an emergency stop then power should be removed. Just removing the RUN signal isn't compleltely safe.

Killing power to the VFD isn't ideal but in a true emergency then it's what you want to happen. It can be done safely using timer relays to allow time for spindle to shut down safely before power is removed.
Is it really needed.? Well only you can answer this one.! . . . Me i'm happy to isolate the run signal using a relay, Which by the way the IP-M as built into the controller so can connect direct to the VFD.

Drives because you have them I'd stick with and they'll do the job ok but NO they are not good as the AM or EM which are much smoother refined drives. Just because they use a DSP doen't make them the same.!