Seems like if that were the case for vampires then they could easily get around having to feed on live blood by using some kind of heater lol. But the undead are reanimated by magic or whatever so who knows lol

I love this sort of thinking! It's sort of like challenging a long accepted theory. My guess is that these particular vampire characters are like refrigerators in that anything that goes into them is immediately started in the cooling process and fairly quickly the temperature goes back down to the average in the being. Now with the living dead, they are already an enigma. How can it be possible to be opposite ends of a common spectrum at the same time. If they're dead, then they are dead. Perhaps a name change is needed to say, the non-living or the active corpses?

Since there's no such thing, you can pretty much make up any answer you want - it can't be shown to be wrong.

Depends on the source material. According to Max Brooks’ Zombie Survival Guide, the undead have no feeling except the craving for living flesh.

I think some movies (Fido maybe) have shown zombies to feel the impact of weather.

My assumption is that zombies would feel cold to the touch, because at a certain point, for some reason the decomposition process stalled....otherwise they couldn't continue existing. Although, if they did keep decomposing, yes they would feel warm to the touch, because decomposition does in fact release heat.

Vampires would follow the same logic as I used above. It is an interesting concept to think that vampires are just cold-blooded human beings who have to feed to be able to do anything.

Wouldn't the answer depend on the external conditions? Regardless of the heat release that occurs during decay, a zombie that finds itself in the middle of tundra would freeze the remains of its genitals off...