How will a B in AP Calc impact pursuing engineering/CS?

I’m going to be frank and say that IMO it depends on the school. Some of the more technically focused programs do say that they focus on STEM grades on a HS transcript. Others will be more forgiving.

I also agree that if you can get a 5 on the AP, the class grade will matter less. Hopefully the exam went well for you!

That all said, I wouldn’t lose sleep over it. Reaches are reaches even if you had a perfect GPA. Build your list realistically for your safeties and matches and you will be fine!