Moss/perlite doesn't sound too standard for Nepenthes...
Anyway, Orchid mix is just that: made for orchids. Nepenthes
have much smaller roots which are easier to damage on the large
pieces of bark used for orchid mix. I use clippers to cut pine
bark nuggets down to pieces between 2 or 3 cm long or so. Then,
mix the chopped bark in equal volumes with peat:sand/diatoms:perlite/
styrofoam at 1:1:1. This makes for a very good Nepenthes mix
which many different species enjoy. Depending on your contions,
you may want to add more peatmoss for more water retention (I do).
To make Heliamphora mix just use this mixture and perlite somewhere
between mix:perlite 1:1 and 2:1. For Helis it couldn't hurt to
make the bark nuggets even smaller.
Dave Evans