A Kick is not something that you "absolutely need". You can have a perfectly enjoybable vape without one.
It does have it's advantages. Without a Kick, your vape experience will gradually fall off from the beginning of a fresh battery until it the battery needs to be replaced. This is the effect of the voltage drop off. As the battery weakens, the vapor quality will drop.
With a Kick, you get voltage regulation. It essentually turns your mechanical
mod into a regulated
mod like a Vamo or ZMax. It's a drop in module that allows voltage regulation to keep the vapor consistant from the beginning of the battery until the end. It will also allow variable voltage. It will also offer the electrical protection against electrical short circuits. It makes your mech mod safer.
Since the Kick does take up some room in the battery tube, you will need to step down a battery size - from an 18650 battery to an 18490.