For maintaining boas, you don't really need night-time drop. For breeding you may want it, but for your young boas it isn't necessary.
Helix and Big Apple offer PROPORTIONAL controllers. That is, current/voltage is pulsed to the heater as often as necessary to maintain your setpoint with little variation. The Rancos are classic thermostats - they turn off the heater as the setpoint is approached and don't turn it back on until the temp drops a certain amount. This deadband amount is 3 or 4 dgrees for Ranco thermostats, and is adjustable from 3 0r 4 degrees to about as much as you want.
You can see from the above that a Ranco will cycle the heat pad temperature by 4 degrees quite a bit. Say you set it for 82 deg. The heat pad will hit 82, then turn off until it goes down to 78, then go back to 82.. all day long. For heat pads, I think proportional is the way to go (or else a dimmer like you have on your human heat pad.) Any proportional controller or classic thermostat requires attaching a probe (heat sensor) to the heater. The probe can't be knocked off or else your pad will be on full. For heat pads that are inside the cage, a dimmer is nice because no probe is needed.
As for nightime drop, Big Apple and Helix offer the function. My opinion though is to simple turn off the heat pad but keep the ambient temp in the 75-80 degree range. I don't know what kind of cage you are using, but a red heat lamp or ceramic bulb works great for air heating. Then a Ranco is perfect for preventing overheating. I use a Ranco on a 75 watt red heat lamp in a 3ft x 2ft cage to keep the air temp reasonable in Winter and early Spring.
Remember that boas come from warm climates where the temps stay within a fairly limited range (there are exceptions like Argentine boas which can experience cool temps in the wild). Having a warm heat pad in a cage with cold ambient temps is no good for a boa. Better to have a background temp of 75-80 and a heat pad or other basking spot reaching up to 85-90 during the day. As adults this is perhaps more imperative than as babies. It may take only one 11x11 heat pad to adequately heat a baby boa. A 6ft boa though needs warm air throughout the cage pretty much, or a big heat pad or large floor-heated area.
Make sure you have a way to keep the air in the cage above 72 degrees whichever method you use or if you use night-time drop.
