drives me freaking insane. If you’re in DFW I will pay you to come to my house and teach me. I’m at my wits end.
Hi there and welcome!
I think the guys are getting you well covered so I'll take a slightly different perspective that may also help you.
While you are figuring out your smoker, smoke some meat that absolutely does not care what temp you smoke at so the fluctuations don't have an impact
Pork butts don't care what temp you smoke at. Neither do full packer Briskets.
Throw one/some of them suckers on and let the temp go up and down from 200F all the way to 400F. These meats won't care!
You can play around with all of the suggestions here and when those cuts of meat are TENDER then you pull them. They are cuts of meat that are ready when they are tender.
At a meat Internal Temp (IT) of about 205F stab the pork butt all over with a kabob skewer and if it goes in like butter all over the pork butt is tender and therefore done!
For a brisket, measure the temp in the thickest yet center most portion of the Flat (NOT THE POINT) and when it hits an IT of 198-200F stab all over with a kabaob skewer and if it slides in like butter then the brisket is tender and therefore done, if not then let the IT go up a degree or two and try again until it passes the tenderness test and is done.
Finally, both of these cuts of meat can handle quite a bit of smoke pretty well so as you are learning how to manage your fire you may get good smoke and not so good smoke but chances are you won't overpower these big cuts of meat unless you run for hours upon hours of thick white (bad) smoke.
That is my 2 cents to help you out while you are learning your system :)