i use AcuRite brand thermometer/hygrometers, this one and this one. i have the probed thermometer's probe at the bottom of the warm side underneath the substrate; that's where yours should be, too.
thermostats will always be the better option to a rheostat. personally i use a rheostat for my CHE, but my room is stable enough and i've messed with the dial enough to know what works.
with a thermostat for the bulb: hang the probe and inch or two above the substrate inside the enclosure and dial it in, or hot glue a cable clip to the inside of the enclosure wall and use that to keep it in place. the reason this thermostat probe can go inside the enclosure is because it will be off the ground where the snake will very likely never mess with it.![]()