I am new to electronics and for my first project, I am using an esp8266 12 e WiFi chip to put together an air sensor web server. My breadboard prototype works but I want to add some other sensors which require 5v. So I need to power the chip at 3.6v and some of the sensors at 5v. I am planning on getting a power adapter plugged into mains and then a buck converter or 2 to get the required voltages. If I get a 9v power adapter, I need 2 buck converters. If I get a 5v power adapter, I only need 1 buck converter. However, I am aware that there are minimum voltage differences between the input and output voltages so am not sure if this will work, given that 5v is kinda close to 3.6v.
I found this pdf which seems to address this question. However my inexperience is making this difficult. Can someone with more experience either 1) tell me if the voltage difference is big enough, or preferably, 2) walk me through the maths in the pdf to arrive at a conclusion?