Meat – Should I trust the Instant Pot or the ThermPro digital thermometer for temperature

Accuracy of the temperature is going to vary by oven, so there's no definitive answer there. As GdD said, you'll just have to get a thermometer and try it.

However, I think this will probably work fine for most sous vide applications. While sous vide is all about precision, a couple of degrees fluctuation isn't going to make a huge difference for most preparations (eggs are a notable exception), particularly given the thermal mass of the water. You could also throw a pizza stone or something in the oven too to help keep a more constant temp.

I think your temperature range is good. 155 to 160 is a good place for thighs. You will need an hour to an hour and a half. As long as you don't drop into the danger zone you will be fine. You could just check a thigh with a probe thermometer at the end of an on-off session to see where the temp is. Sounds like a bit of a pain, but certainly doable. One caution...that looks like a small pot. If you are doing more than one or two thighs, you will crowd the bag and might not achieve even cooking...this could create a danger if the center of the package did not reach 140. Advice: Get a circulator! If you enjoy eggs, for example, the price is worth egg cookery alone, in my opinion. :-)

By the way, while many people prefer this route toward fried chicken, I actually have had the best success with, and prefer Keller's Ad Hoc recipe.