1) actually, yes. Good quality charcoal is hard, and shiny, with no remaining woody smells. Poor quality charcoals produce soots and dont burn nearly as cleanly as good quality charcoals.
2) A charcoal maker balances burning some of the wood to make the heat to pyrolize the rest of his load, against the loss of that wood, since it could be charcoal instead. An unskilled maker will waste much of the load with an inefficient burn, and produce less, and lower quality charcoal. A skilled maker will burn significantly less, but gain considerably more of the load as charcoal.
Example-- A proper kiln design traps more heat than it allows to escape, so even a tiny heat source will eventually make an ideal kiln fire. (like a candle.) this assumes a perfectly refractory material, and a perfect flu design. Those are both impossibilities, so we cant reasonably expect to fire a ton of wood into charcoal, using a candle flame.
What we can expect, is to fire a ton of wood into charcoal using a hundred pounds or so of the wood, instead of half a ton.
When it comes to charcoal production, production that is slower is better. Wood contains chemically bound water, which under the pyrolizing conditions of the kiln, will chemically combine with carbon, and produce "Syngas"- a mixture of reduced water in the form of hydrogen gas, and carbon monoxide. This actively removes a fair chunk of the charcoal's mass if you dont control the reaction. Firing the load slowly allows the water vapor to escape up and out the flu, before reaching a reactive temperature that would deplete the carbon of the load. Basically, you hold the kiln at about 420F, and just hold it there for a very long time. This drives off the water, but is under the kindling point of the wood, so it doesnt chemically combine with that water to form syngas. The slower fire doesnt need to be as big, since the kiln isnt kept all that hot. (It's just good pig roasting temps! BBQ!) Once the load stops gassing, you totally seal up the saggar, and heat it up to 450ish, and hold it there. Then the magic happens. Usually, they pyrolysis of the wood itself is sufficient to keep the reaction going for the most part, so input fuel is actually reduced once the ideal target temp is reached. Keep it covered and insulated for a full 36 hours or so, until it cools.
unload, and enjoy your charcoal.
(That's the very simplified version. Skill and technique will have considerable effect on the quality and quantity of the finished load, just as the OP says.)