I have a lang 48 not the 84 so your fire management should be similar just bigger.
I split this size chunk in 2 pieces
when the fire looks about like this, lay the chunk on the grate and then push it back with a poker as far as I can. If I want it to run hotter put the piece in sooner, cooler wait a little longer. 250-300 is my normal range using hickory or pecan vents and damper wide open on the factory lang grate. Haven't tried any charcoal yet. Once again I only have the 48 but when I bought it Ben Lang told me to run it wide open and so far so good.
Smoke Shack, Lang 48 patio, cheap charbroil charcoal grill, weber chimney, thermoworks rt600c, mav et-732