I just did 2 separate hot & fast smokes on my Camp Chef this weekend, air temp was in the low 20’s on Saturday & low 30’s yesterday. The Saturday smoke was two boneless butts at 275 for 6 hours & I had no problems maintaining temps. Last night was a meatloaf at 300, same results, no problems maintaining temps. I honestly didn’t watch the smoker like a hawk but anytime I looked at the controller I was within 5-10 degrees of target temp. I did try to fire the cooker up Friday night to make pizza but barely hit 375, it was single digits with gusts into the 20-30 mph range so I gave up. Generally speaking my pit is pretty close without a lot of crazy swings so maybe you might have a problem with your unit that Camp Chef can walk you through over the phone?
I think way too much is made of temp swings, my old offset smokers would swing way worse than the pellet grill until I got my WSM, that was rock solid all the time but anyway the point is that you can drive yourself nuts on temp swings, especially in the cold weather. You can try the blanket from Camp Chef & see if that helps first? If not the PID controller may be your answer but (IMO) I pay less attention to the controller read out & make sure the food that comes off the smoker is good since that’s why I smoke. I sleep a lot better at night once I got that in my head!