I referred to this chart often when I first started developing my own recipes. It's certainly not amounts that are set in stone (as IL & Susie pointed out ) but it is a good starting point.I remember reading something like that on soap queen blog, let me see if I can find it for you.
Here it is,
You can, but those numbers do not tell you how the soap feels. You need actual soaping experience to be able to convert those numbers into skin feeling. No one can tell you whether you will like this more than that. You must make the soap and try it.Alternatively you could always plug in different fats/oils into "soapcalc.net" and see the general qualities of the bar you could make.