I may be mistaken since I do not have a lot of terminations in front of me but I have usually found that most terminations are rated at 75 deg. The CH breaker I am holding in my hand right now has a dual rating of 60/75 deg. I will be paying more attention to my terminations in the future for the rating but I'm certain most are 75 deg. I very rarely use the 60 deg column.
In wisconsin we do not have to derate per Table 310.15(B)(2)(a) for residential wiring.
Table 310.15(B)(6) is simple to understand. If you calculate you need a 100 amp service you are allowed to use #4 wire instead of #3 and I believe this is mainly allowed because it is residential and the loads are intermittant and almost all non continuous unlike commercial and industrial.
Base your circuit ampacity on the 60 or 75 deg column (determined by your termination) and your conductor ampacity for derating and correction on the 90 degree column and use thhn wire. Hope this helps.
Ron
