No problem...What you say is true. With cooking in general, meat cooks slower at low temps and faster at high temps. You set your Oven to bake a Cake, the bottom of the oven is going to be hotter and the top a little cooler so the Sweet Spot, where the Cake bakes best, is in the middle. Now with smoking meat items like, Pork, Beef, Chicken, and Hot Smoking in general, a Range of temps with a desired average temp is perfectly fine and finding that sweet spot is not as critical. You will get a similar result cooking at a steady 225 for 8 hours or 8 hours at a temp Range of 200 to 250°F, resulting from temp swings while trying to maintain the fire, air, etc. You just try to stay close to 225 as much as possible by learning your smoker and how big a fire to maintain and how. So, for a single Roast you wish to smoke at 225, find the Sweet Spot but don't sweat it if the temp swings a bit.
When maintaining a steady temp becomes critical is with Cool Smoking like Cured Sausage, Hams, Bacon, and such. A typical Kielbasa Recipe will call for smoking at 130°F for 1 hour then bumping the temp 10°F every hour to no higher than 170° and holding steady until the Internal Temp (IT) of the Kielbasa reaches 150°F. Anything else and you will have an inferior Kielbasa.
As far as the Mods go, some make maintaining a specific temp easier. Some are designed to get even temps side to side. This becomes more important when you are Smoking 6 racks of Ribs and/or 4 Porks Butts for a big party. Having a Hot spot near the fire and a Cool spot at the other end means you have to constantly be swapping and moving meat around for even cooking at the Desired Temp. I hope this helps, but feel free to keep asking questions. There is a lot to learn...JJ