Strangulation (done (in)correctly) can cut off the blood flow to the brain, which halts oxygen delivery to the tissues. Holding your breath just causes oxygen delivery to the blood to stop. Your body has enough blood and oxygen in it to last for a few minutes without breathing, but only as long as it is circulating to the tissues that require it.

While holding your breath, the ratio of carbon dioxide to oxygen will steadily increase, which will eventually trigger some chemoreceptors and force a reflexive diaphragmatic contraction.

The heat isn’t transmitted via photons, it’s transmitted via convection. The air acts as a medium to transmit the heat energy outward. The heating element itself emits photons because it gets hot enough where the atoms within vibrate at a frequency which reaches the visible spectrum of light. That’s why cooler elements glow red (lower frequency) and hotter elements glow blue (higher frequency). Most of the heat energy is not contained in the photons, you need an output on the level of the sun to achieve that. With regards to the sun, all of the energy is carried by radiation anyway, because convective currents can’t travel in the vacuum of space.

May I introduce you to exurb1a