Water trays for Nepenthes culture works beautifully for some, and may promote root problems for others, depending on the species. The only real problem we've seen occurs when the plants become dependant on a perpertual water supply. The root system can become minimal, as the plant sends down just enough root mass to remain perpetually soaked (usually at the bottom of the pot where it can get this endless supply of water). Once that constant water supply is removed, the plant will wilt. We find culture "on the dry side" to work out better. It forces the plant to produce more roots in search of water, and big root systems equals healthy plants resistant to occasional droughts (the owner of the Nep not sticking to the watering schedule). This is what works for us--with a greenhouse filled with thousands of Neps in a subtropical climate--not the same thing as someone growing in a chamber under lights with timers and humidifiers. I mention this because it is based on the balance of all factors that meet the plant's needs: light, water, media, temperature and air (humidity,quality and movement). So, the bottom line, it's what works for you.
As for northiana: we are finally getting a handle on how to grow this wonderful species and are seeing rapid growth this summer when back in April they were moved from a peaty mix, kept wet, to a very well drained "rocky" mix and allowed to dry out very slightly before giving a total pot drench. They also produce big root systems(even when grown wet) and want lots of room (oversized pots). They like it shady, and constant high humidity.
Good growing, everyone!