One thing I have learned is that the distance from the fire to the meat is very important. IN my kamado grill, the distance from the fire to the meat is about 12 inches. Even with a diffuser/shield to keep the fire/heat from going direct to the meat, 12 inches is too close to the heat source. My old grill, the charcoal/wood is about 18 to 20 inches below the grate, which lets me keep a steady temp at the meat in the 180° - 185° temp range without it going out. In My kamado, the lowest I can keep a steady temp without going out is 200°, but I have to watch it close. Slower cooking and more smoke! Love it.
I grew up with a couple of friends whose dads used old refrigerators and low temps and smoking over 24 to 36 hours.
While I usually do ribs and shoulders/butts, thick steaks and chicken/turkeys, today I smoked my first "eye of round". Pulled it at 129° internal temp and it made the best, tastiest thin sliced sandwich meats. LOML doesn't usually like "pinkish" roast but she went back for more on that.
What thermometer do you use? I have settled on "Thermoworks" and found them very consistent, more so than others.