I've got an old little cheif that I've been smoking in. I tried it out in the back yard on a sunny day, got it up to 150. So, I built a plywood box to put it in. Today, a 40 degree and windy day, I got it up to 160...which was a chore. That little 250 watt element is worthless. I ended up finishing my jerky in the oven (not a big deal). I'm heading to the store tomorrow for a hotplate.
The thing to remember about thermostats, they turn the elements on and off...not a big deal at high temperatures, unless your element is too large for your smoker. Then you are going to get up to temperature, your element is going to shut off, if you are insulated well, you are going to hold at temperature for a while, and your electric fire will go out. By the time it comes back on, you will have cooked devoid of smoke for ten minutes. Learned that the hard way. Guess if you had decent draft through the smoker, it wouldn't be an issue, but if you had decent draft, you could just adjust your temperature by adjusting your draft.
Anyway, you can get cheap thermocouple digital controllers on Ebay if you have any electrical background. That's what I use, more as a temperature gauge than a control.