Which recommendations should I submit?

Hey guys.
So I am taking recommendations from three teachers- my 8th to 10th grade economics
teacher, my 11th-12th grade chem teacher and my 11th-12th grade bio teacher. My intended major is chemistry/biochemistry.
All these teachers know me quite well-in all their classes I am or was the top scorer. They also know well about my ECA involvements and my regional and national level achievements(country-Bangladesh).
Now,most schools need recommendations from “two core academic teachers”. In the context of that, should I exclude my Economics teacher, considering the majors I’m applying for?

Colleges typically like to see recs from a humanities teacher and a sci/math teacher. You appear to be aiming high, so I’d stick with the Econ teacher and not both bio and chem. And remember the rec doesn’t have to be based on you having top grades. Class participation is worth more than the grade in this context. Choose teachers who you really like, and who really like you.

@Lindagaf yup I sure like them and they too seem to quite like me!Thanks for your opinion!

Hey guys.
I was wondering, is it necessary for recommendation letters to have the school’s official letterhead/logo and stuff? I know teacher sign is needed but is that needed too.