OK, humidity above 50% is fine. More is better, for highlanders 65-85% gets you good pitchering without pathogen problems, but for lowlanders humidity generally needs to be higher. Unless you're growing lowlanders like bical, northiana, rowanae etc that need lots of heat and humidity, you can get amazing tolerance from Nepenthes in relation to humidity.
The differences between rajah, lowii and villosa don't relate to humidity. It relates to temperatures. Villosa is less tolerant of warmer temps, especially night temps, than rajah or lowii. Whilst it will grow fine for several years as a small plant in less than idea conditions, the older it gets, the more it needs strict temperature control. Many growers of villosa measure their success in how long the plant survives for them.
Villosa is not a species to be grown unless you've got the proper set-up to grow it in, unless you just want to have it for 3-4 years before it dies.
Hamish