superfat adjustment

Hellooo my fellow soap makers. I've read in a few threads that determining SF is totally up to you based on your preference. However I've also read that certain oils or butters pair well with lower/higher SF. I've also briefly seen SF associated with the term "lye discount".. would someone...

I am going to use 40% for my LC and 4% superfats. What would tweaking with these numbers do? What does a higher or lower superfat percentage do? And if I wanted to use 33% LC like many other people, what would be the biggest difference as opposed to 40? Thanks.

I have a need to "say it out loud" since I'm not quite sure how to define the research to know if it works. I would like to make coconut soap stain bars for laundry and a "regular" batch but hate doing dishes. Is it possible to adjust superfat on the fly for CP? In theory, I would make a...