First off, your CPs look super amazing! Your VFT looks healthy even though it has long skinny leaves, with more lighting newer leaves should be thicker. But for the lighting, I'm not sure but it does seem to work for your plants. Best advice is keep at what you have currently.
When it comes to dormancy, VFTs do need light, but less of it. I'm still new to CP growing and have my first VFTs going in dormancy too (except where I'm at mother nature is taking her sweet old time to get below in the 50s because the average day temp rn is low to mid 70s and lows 50s at night
), but I would think that 6 - 8 hours of light for them during winter would make sense. And it depends where you live, if you live in a tropical climate or like you said in a desert location where it stays warm and there's hardly any temp drops, then you can do the refrigerator method. Or you can move it to your basement or somewhere colder that stays below 48 degrees until spring.
I tried my best to help, hopefully what I said does!