The idea that thermometers and hygrometers are useless and should be thrown away is rediculous. So all tarantulas from all of the places all over the world just happen to thrive in not a set Parameters but whatever feels right to you the keeper. Does not make sense.
Tell that to all the people who killed their avics with to much humidity or the same for the ggbs. The same can be said for burrowers and swamp species. The fact is we don't know yet. We don't have enough data. And for every spider who's death was a mystery we see how little we know. I tend to take the advice that most Ts do well 70-80 and 30-60 humidity. Slings def need humidity depending on the species. Careful who you listen too. Next they will tell you all t bites feel like bee stings. Goodluck