There is some small moisture content in black powder so there would be some H2O in the combustion products, plus if there is any hydrogen left from the wood the charcoal was made from, that also would oxidize to water. Quoting Wikipedia, "The burning of gunpowder does not take place as a single reaction, however, and the byproducts are not easily predicted. One study's results showed that it produced (in order of descending quantities): 55.91% solid products: potassium carbonate, potassium sulfate, potassium sulfide, sulfur, potassium nitrate, potassium thiocyanate, carbon, ammonium carbonate. 42.98% gaseous products: carbon dioxide, nitrogen, carbon monoxide, hydrogen sulfide, hydrogen, methane, 1.11% water."
The majority of the smoke is the solid products in finely dispersed form. The water vapor may condense as the combustion products expand and cool but the quantity is so small that I doubt there is much visible as steam condensate.
The addition of flour mixed into the powder would likely cause the powder to burn less efficiently as there already is barely enough oxygen to support the combustion of the sulfur and carbon and hydogen of the powder's fuel elements. Once the flour was dispersed into the air and oxygen was available in large amounts, the flour might burn if the temperature and density were correct.
