I use a refrigerator. I control my temperature in the Incubator, the Humidity I control in the EggBox itself. My first Incubator I made worked for Geckos, it used an aquarium heater, an ice chest half full of water, and a rack to keep the tubs out of the water.
The next one I made was a ice chest with a cheap thermostat and flexwatt.
Now I use Full size refrigerator I got for free, 17"? Flexwatt and a Helix. Looking back I wish I would have made the refrigerator years ago. BTW the fridge was cheap, and took less then a Hour to setup, Works GREAT.
Whatever you chose, good luck.