Hello Turner
Welcome to the forums!
One problem you might run into by growing so many different plants in the same terrarium is that each one has its own cultivation requirements and those requirements may not match. For example, your VFT will need dormancy which means cooler temperatures and shorter photo-period. But your nepenthes wouldn't tolerate those conditions very well. I don't know what nep or sundew you might have but one might need stronger light than the other or higher humidity. Unless you really like the look of plants in a terrarium, they don't NEED to be in one. A VFT will do just fine in a pot. They don't need real high humidity. And most sundews can be acclimated to grow in less humidity than you might think. (I have sundews both in tanks and also growing openly on a shelf.)
In my experience, I have had better success with plants individually potted as they can be "handled" easily when something needs to be done (repotting, trimming, pest/fungus treatment). Also any plants with pests or fungus can be easily separated from the rest and then returned when "cured."
VFTs need dormancy. The general rule of thumb is Thanksgiving to Valentine's Day although that's not an iron rule by any means. Basically, your plant just needs a couple of months of rest to store energy for the spring growth. My VFTs are outdoors so dormancy is taken care of by Mama Nature. Some people use cool basements, garages or refrigerators for dormancy. My outdoor plants are still green and still have traps but are worn-looking and not growing. By spring, hard freezes will have killed off most of the traps but the bulbs will be fine.
Your nep does not need dormancy. I don't know about the sundew without knowing what it is.
Make sure you are providing all your plants with a lot of light (NOT incandescent bulbs). Sunlight or fluorescent lights work well. And use pure water for them all (distilled, R.O., rainwater).
I hope your plants do well. Stick around and have some fun.