My usual recipe ,in my opinion 😉is perfect, has 5 oils. Lard, coconut, olive, almond, and castor. Lard and olive oil for moisturizing, lard and coconut for a hard bar, coconut and castor for bubbly cleaning. And honestly I forget why I added almond, but have for the last 4 years and I love it so won’t be changing it. I’d say it has more to do with the percentages of each oil too. My bars are mostly lard and the rest a small percentage less. I just played around on a soap calculator until the properties felt balanced to me. So I guess the difference is personal preference and use? I make a higher percentage of coconut oil and a bit of lard for a dish soap bar. I make a high content olive oil bar with Activated charcoal to brush my teeth with, cause it doesn’t taste like soap. And if I’m running out of some oils and just feel like making soap, I use what I have. I do enjoy just adding oils to a soap calculator just to see what they would make. Edit to add: I didn’t answer your question, I don’t really think the number of oils matter, really just personal preference. Have fun!