Do you mean your computer overheats when on campaign map?

I always noticed how in Warhammer 3 my rtx 3070 ti goes up to 79c when i am at the campaign map when in battles is always like 65c. Also my cpu i9 11900kf got hot into 80c when only in the campaign map

80c is generally fine for gpu, a bit high for CPU. I think your case has airflow issues. Consider checking CPU thermal paste. I had something similar with Witcher 3, where fans would go crazy, turns out specific spots of gpu would get ultra hot, applied new thermal paste and temps went down.

The campaign map is more intensive on GPU than the battles. All you can do is reducing graphics settings or improving cooling in your computer by more fan speed and clearing out dust.

My 3060ti used to reach 90c on campaign map. I recently changed to 5070 and it stays cool (no more than 65c).

There should be separate video settting for campaign map quality. It's weird that is uses much more gpu than a fight with like 6 thousand units or even more. But is has been like that for all recent Total Wars I think.