I use cool mist because the herp can't get burned by the output of mist. But more heat will have to be pumped into the enclosure to make up for the cooling effects of evaporating droplets.
Thermostats are very helpful to regulate the temperatures in humidified habitats. I use Spyder Robotics Herpstats, which are dependable and safe because they are solid-state. I've seen ads by Zoomed for thermostats that are less costly.
How about getting a ceramic heat emitter(s)? They last 10+ years.