The IG and N methods are the only ones that can achieve a solid 10/10 in peacefulness imo. N has only one downside, its taste, but it's easy to just pinch your nose and have a tic-tac.
SN is likely overrated to some degree too.
I don't think it's overrated; it has possible uncomfortable side effects in the first minutes yes, but once past that short time, it knocks out pretty quickly and is very effective. I believe the people who experience more discomfort (or even failure) don't follow the protocol, even if its not that hard to just fast and take antiemetics. Having benzos on top of that might give an upper-hand to those experiencing crippling anxiety though.
SN popularity is understandable because it
was easier to source than a gun or opioids, and less stress inducing than hanging or jumping from a building for example. Even though it's not that easy to overcome SI and drink it, it still is a cheap alternative that many consider peaceful
enough to CTB.