You don't have to put them in a terrarium and Neos are quite humidity tolerant. Lighting is still important and in the wild, have exposure to longer winter light hours than in the summer. I keep mine either just below, or right at Catt growing lighting requirements and lessen water in the winter. I too have Neos still in spike and flower. Just keep watering them as usual, and when they're done flowering, reduce the water for winter.
I switched to LED's a year ago but I used to grow mine with a 4 ft 4 tube T5 fixture. At first I had the fixture about 2 feet above the plants. Then I ended up putting reflective mylar around the grow rack to see if I could get better light coverage on each end. The mylar increased the light levels overall so I moved the fixture about 3 feet above the plants. I had the lights on for about 12 hrs/ day during the winter months and light levels measured 800 - 1000 fc.