That one is easy - Kevlar is strong, fire resistant, and has become pretty cheap.
Like this source:
https://www.amazon.com/gp/product/B0184ZGSQ2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
It's not "too much" shock if it doesn't break the shock cord, nor the anchors to which said cord is tied. Braided Kevlar satisfies these requirements in spades.
Nylon cords are, unfortunately, lack all the positive characteristics of Kevlar: they burn, then can break from over-stretching.
Case in point - I made the mistake of flying my first Estes 1:200 Saturn V with the stock daisy-chain of Kevlar and nylon. One the second ascent with a Quest motor, the nylon broke, and nose cone drifted into the next zip code. The bulk of the airframe came down ballistic, narrowly missing a parked car.
You can bet I had gone back and 3x check all my Low-power rockets to purge them of any remnants of nylon or stretch cords.
HTH,
a