It is not the wire size that determines the temp-rating you can use.
It is either the size of the terminals or equipment that requires above or below 100 amps that determines the temp column to use unless otherwise marked.
110-14(C)(1)(b) Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than 1 AWG, shall be used only for one of the following:
(1) Conductors rated 75°C (167°F)
(2) Conductors with higher temperature ratings, provided the ampacity of such conductors does not exceed the 75°C (167°F) ampacity of the conductor size used, or up to their ampacity if the equipment is listed and identified for use with such conductors.
I would be very surprised if you can not use the 75 C column.
I am confused with this.
The MCA for the heater strip supply circuit is 110amps. The max breaker is 100 amps
The minimum circuit ampacity can not be higher than the maximum breaker size.