I am not an LEO but have Axom/Taser knowledge. I actually knew about this company right when they developed M18/26 from being working in a financial company.
The taser has about 1ft spread at approximately 7ft distance. On some areas of body, 1ft prong spread is not as effective. Best distance seems to be at around 10-14ft static target.
Back works better, because there are many muscles on the back, and target is larger than front (need to watch for an eye, and face etc). Taser products are great, because it has just the near ideal voltage, and perfect pulse rate for Neuro-Muscular Incapacitation (NMI).
Personally, I would not deploy taser when someone is running, especially when turning left and right on tight corner. I would also avoid areas like stairs, tight concrete walls, or anywhere where subject can just hit their head and break their neck.
When contacted properly, it DID NOT make those TICK TICK TICK TICK sounds like youtube video did. It was silent, and subject hit the ground like a sack of potato (dead weight) without any sound.