We are all still learning as breeding BPs is still relatively new, that's why there is a lot of different advice
If you are substrateless (using light diffuser/egg crate on top of perlite/vermiculite) just make sure it's really wet and close the lid. To be completely honest I have never measured the humidity in my egg tubs, I just make sure the perlite stays soaking wet, but not enough to splash on the eggs when the tub gets moved. Also, those cheap $1 shoe box tubs (what I use) are not air tight so the eggs can still "breathe".