the powder is some form of baking soda or chemical equivalent. certainly won't kill you, or be as remotely unpleasant as CS,

Yes, powder is usually sodium bicarbonate with some talc to make it more quick. Sodium bicarbonate produce CO2 when heated so its fog is able to extinguish flame.

It is not reaaly toxic, and hardly inhaling that powder for few minutes will have any long-term consequences, but it is definitely not very healthy to breath it, just because it is not what humans used to breath.

but you don't just stand around in it after spraying one around a room. no one in the vid is sneezing or rubbing their eyes.

It is not an agressive thing. And it is very thin. So no sneezing or eye irritation.