A&M looks at a variety of factors: class rank (not specifically GPA) and everything submitted with the application - outside activities, leadership, employment, the essays, (test scores if provided), etc. If he decides he wants to send in his test scores, they will be included in the review process.
The number and types of different offers depends on many variables how strong that particular group of applicants is, how much room there is at that time for the different offers, etc. It is very, very early in the process since applications are not even open yet. Choice of major is not a factor for freshmen admissions. Plus we are all in uncharted waters due to the virus.
He can read details on the change of curriculum from Galveston to College Station at
https://www.tamug.edu/admissions/Change_of_Curriculum.htmlHe really should call an admissions counselor at 979-458-0950. They can discuss his particular situation with him. They can discuss his interests and help him understand the different majors he is interested in.