It's not ideal to add any heat into your telescope system, because it induces tube currents which degrades the image you see in the eyepiece. Unfortunately though the alternative is dew on your optics and an early night.
In a Newtonian the secondary is quite prone to dew as it's close to the end of the tube. I added a removable 12" light/dew shroud onto the end of my tube. It may have helped a bit, but my secondary still gets dew on it without the dew heater.
Heating the primary is not recommended. Lots of people go to great lengths with fan systems to cool the primary mirror so its temperature is closer to ambient. The boundary layer of hot air that sits on top of the mirror is what is responsible for the degraded images when a telescope is first set up. Cooling the mirror with fans helps clear this layer. So adding a dew heater to the primary defeats the purpose of having cooling fans. Fortunately I find the primary rarely suffers from dew problems as it's at the rear of the tube and somewhat protected from the cool air. I run my fan system constantly while observing which forces air up the tube and out the top. This I think also helps prevent dew problems.
I have a dew heater attached to the back of my secondary with silicone. I have attached copper strips to each side of a spider vain. They are a bit hard to see because I painted them black. I then soldered the heater wires to each copper strip. At the tube end I soldered wires from the copper strip to an RCA type plug that I fitted through a hole I drilled in the tube.
From the outside this is the lead running from the dew controller to the RCA plug. Any of the heaters you have linked there from Bintel will work fine and have all the bits there to do the same as I have. Except the RCA plug, I got that from JayCar.