You might want to read the Double Degree Dilemma essay in the Read Me thread pinned closer to the top of this music forum. It uses hypothetical individuals to illustrate different ways to study music. (It does not include the option of majoring in something else and continuing lessons and extracurricular performance.)
Basically the options are BM, BA ,double major or major/minor, and double degree. A BA is 1/4-1/3 classes in music, and a BM is 2/3-3/4 classes in music.
A BM usually involves audition, and a BA usually doesn’t. But you can submit a music supplement with recording/video, music resume and letters of recommendation related to music.
Composers do fine with either degree. Some BM composition programs require an instrument, some don’t. Some BA programs have a performance component, some don’t.
At the undergrad level, we always felt that diversity of student works is important, because it shows faculty is allowing students to develop their own “voice.”