70% is fine for most nepenthes, some ultra-highlander species(like N. Rajah) need 100% humidity at night

Be careful with humidity that high or higher, not only does it increase the risk of mold killing or damaging your plants, it also increases atmospheric molds which can cause sickness, dry coughs, and allergies. Your plants should be healthier and stronger and bigger. I actually have my plants growing currently in like 25% - 50% and after about 3 - 5 weeks they adjusted and began growing better than they had in the nurseries (all except my raffelsiana what do you all recomend for that one?).

N. Rafflesiana need high humidity or else they will not do so good, this is all to my knowledge. I have never grown N. Raff, but i have heard that it needs high humidity. I don't think you should ever get your plants to 100% humidity because as you said it increases chances of fungus.