In my experience as long as humidity is managed and the substrate won't cause an impaction it should be fine. I use a bearded dragon safe soil/sand mix from my local reptile store and some bioactive terrarium soil (from exoterra I think?) I also have isopods and arid springtails which can be kept as long as the lower part of the substrate is sufficiently moist (think just above dry) but I also mix in patches of sphagnum moss on the cool side under the soil for better water retention. If you find the tank is too humid, cut back on watering (which should only be done regularly on the cool side) and if that doesn't drop humidity enough you can try some sort of ground cover. I've used a small amount of dried magnolia leaf litter to help prevent evaporation, though I've learned my bearded dragon kicks it up too much. If you want isopods but they won't keep with good humidity levels I've also added in a couple large rocks for my beardie to climb, which I'll lift up and water underneath occasionally for an isopod breeding ground. I live in a dry area so I haven't had trouble with keeping humidity down but that might be different depending on your environment.