One thing to understand is soap ingredients are very subjective. The "rules" are too. Take coconut oil, as a general rule under 25% some say under 20%, but you will find people on this forum who love and swear by recipes that have 30% coconut or more!
To start out follow the general rules, but as you go along don't be afraid to push the envelope and see what happens. It is sort of like baking a cake, some people substitute apple sauce for the oil, some say it makes a cake too soft, some like cake flour only, some use a mixture.
The whole idea is to find what you like, and that may be very different from what I like or others like. This is one reason soap making is such an awesome past-time, it is always changing, never the same. You can make soap for 10 years, then someone comes along with an experiment that changes the whole way you think of things.
Bottom line is this is not an exact science. It is more like a blend of art and science.