My experience is that the radical swings come when I load the cold meat into it. It comes back to temp pretty quickly, but will vary for a while. As time goes on, it will settle in and purr. The more that I cook on it and get that dark seasoning, the better it seems to have become.
I do use a 3 ft length of 5" pipe with an elbo facing down. this get it out from under the deck cover and air doesn't affect it. It is on the North side of my house and we have had it going in below 10 degrees with very good success.
Finally, I do get the fire pot really cleaned out after each cook. Then when I start it back up, I put a few pellets in it to give it a jump start.
the only time I had a lot of excess smoke, and I mean a lot, was when I was at a comp and had finished the Friday night dinner cook, turned it off for a bit, did not clean it out and restarted to quickly. The pot over filled and things were crazy for a while until we got the pot cleaned out.