Well, I have used neem oil successfully to treat mites on nepenthes before. Smells bad for sure, and reduce the amount of light the plant gets for about a week after treatment, since the chemical makes the leaves more photosensitive. Nepenthes are pretty tough when it comes to chemicals compared to most CPs, but I can't guarantee that what you have used on other CPs successfully won't harm a nepenthes.
Dilute the neem oil with distilled water before use, making sure to check if you have bought the concentrated stuff. If you did, there will be instructions for dilution. Since the mites can be in the soil too, I carefully remove the plant from the media (it's fine to leave some on the roots so as to not cause a worse disturbance), and dunk the plant top first into a mixed solution of the neem oil and distilled water (shake well before use). Just dunk it so that the entire plant has been exposed, no soaking needed. Neem oil doesn't kill the mites on contact (it messes with their reproduction and growth), but they do hate it, and you'll probably notice a ton of adults popping off the plant once they are hit with neem oil. Repot the plant in fresh media and a clean pot, spray down the soil with neem oil, wait a day or so, and spray the exposed foliage with distilled water. You don't have to do the distilled water spray, but it helps reduce the damage to the leaves that neem oil can inflict. Retreat after 1 week for the best results... and keep the plant away from where it caught the mites to begin with.
Never use neem oil if your plant is going to experience temperatures above 90 degrees (probably not a good idea for lowland nepenthes).
That's the best advice I have to give.