I will apologize in advance for very complicated answers.
Water holds a lot of heat (specific heat is thermal heat per unit weight). You could start by adding 2 gallons or 20 gallons of boiling water, and there would be a lot of heat held in there. This would create a lot of thermal inertia, and it would be resistant to spikes or dips in temperature. All good?
Water boils at 212 degrees Fahrenheit. This means that the water could be boiling, but until the water is gone, the water boiling process would be pulling extra heat out of the smoke stream and essentially cooling the smoke. This would work to temper or stabilize the temperature of the smoke stream. (again, only until all the water had boiled off) This would limit the amount of heat that would be transferred from the smoke stream into the meat. The amount of heat is directly related/proportional to the temperature difference.
Not totally sure, I'm an engineer, and fan of Q. (Not a pit master.) But this I do know. A lot of the thermal energy in the smoke stream will be required to boil off the water, so a lot of water will require extra fuel. I speculate that a couple of gallons of boiling water as the fire settles down would help more than hurt. (It just seems that good Q will always take a long and steady and exacting burn, but a lot of good pieces of meat get ruined in the first half hour. You also would not want to start by adding boiling water in a cold smoker. Condensation on the walls could rain down soot and rust onto your meat.)
still converting my $30 offset smoker into a reverse flow