Full disclosure - I first learnt about this from this article
I have a view that thigh meat is best at 80c and breast somewhat lower (I like 65c). Happily if you spatchcock a chook or roast it upright or on a rotisserie you can often get both these temps in one cook.
Some people will say that “chicken isn’t safe unless cooked to 74c”.
Well that’s not entirely true.
So before we go further you need to know that that temperature and time are the two factors that make food safe. The 74c rule is created for dummies as that is the temperature that salmonella is killed instantly. This eliminates the time dimension and simplifies things.
For those who are more thoughtful and diligent in their cooking (and since we are on a cooking forum, that presumably includes you!) you can use both dimensions, time and temp. And we are multidimensional cooks!
So, here’s the USDA guidelines that explain how these two dimensions work.
And here is a relevant table from that document.
So now we can see that a diligent cook can take breast to lower than 74c and still be safe.
Like the article above and many people on this forum say, breast is best at a lower temp unless you like it dry and tough.
I’d be interested to hear from others about what temps you recommend for breast and thigh?