The reason you are getting humidity suggestions that are all over the place is because incubating is an art. Temp must be dead on but humidity is subject to what part of the country you are in, the room humidity, the outside humidity and what time of year you are incubating. What works for someone in New York would not work for me. You will spend years trying to get to that sweet spot. Hatch rates also depend on if you are using shipped eggs or local eggs. What type of incubator you are using will also dictate how much humidity you need as well as the type of egg you are incubating and how many eggs you have in there. I do things differently in my styro incubator than my all plastic one. I weigh my eggs to determine if I need to increase humidity or back it off. If you don't want to do that, then you need to watch the air cell closely for proper loss and make changes based on that. IMO it is a bit better to go a bit less humidity than too much and take the chance of getting your chicks to hatch date only to loose them to drowning.