be careful of electronic hygrometer/ thermometers some of these are not made to handle the incubator's humidity for a long period of time. I have tried a couple purchased from walmart, and both would stick at 96.8 degrees when the temp was 99.5. also just because it is digital does not make it right. look at the back of the package, most have a 1/2 to 1 degree variance.There are a lot of cheap thermometer/ hydrometer combos out there. As far as humidity levels and higher humidity vs. dry hatching you will just have to see what works for you. Incubating eggs successfully can involve a lot of trial and error while you find what works for you and your incubator.
Here's a dry hatch guide: https://www.backyardchickens.com/a/how-to-incubate-hatch-eggs-using-the-dry-incubation-method
i had several little giant thermometers laying around, i put a few of them in the incubator and took the average. then i marked the ones that read that average temperature for use. these seem to be working well for me. you can pick them up for about a buck anywhere.