I am trying to connect a '2 relay module' to a bulb and mains so that when the temperature goes below a certain point it turns the bulb off and when it goes above a reading it turns it off.
Make sure you use a relay module designed to switch mains voltages and to isolate them from your control circuits. Don't leave any mains conductors exposed.
To switch your bulb on and off do not use a single temperature value or your bulb will flicker on and off as the temperature rises slightly above and falls slightly below the value. Instead have an "on" temperature setting and an "off" temperature setting with a decent gap between the two. Your bulb should come on when the temperature fall belows "on" and stay on till it rises above "off" it then stays off till it falls below "on".
The same applies to humidity, you don't want to be continuously inputting tiny amounts of water. What you want is for the humidity to oscillate slowly within a comfortable environmental range for your reptiles.