Ours isn't even that hi-tech. it has a grate with a reasonable airflow, which is shut-offable, but still leaves the holes in it, so if we want to definitely burn just wood, we don't bother to empty the ashpan, hence there is a solid bed of ash. If we want to burn coal (pretty rare, but its easier to keep going overnight with coal) we empty it properly. It has primary, secondary, and tertiary airflow controls. We always leave the tertiary one fairly well open, as this is what allows it to digest its own snot and you can see the combustion take place around the tertiary air inlet holes, burning nice and clean.
Ours is not an expensive one, its a Hunter of some sort, but its a clean burn one.