If you use your personal email address your contributions will be perceived as having much less vallue, than if you use your institutional email address.
By submitting with a personal email, you are identifying yourself as an independent scholar. You are an undergrad, and I presume that you have earned no post-graduate degrees. The work of an independent scholar has some authority, if that scholar has been awarded a PhD by an accredited institution. The work of someone off the street, with no credentials, has no merit.
Having worked at a university, I will add that use of the submitter's institutional email on submitted work is usually required by the receiving member of the faculty, and is always preferred by faculty.
Since you are submitting your work to an academic journal, and the relationship between this journal and any institution is unclear, then it is unknown whether those at the journal have the same expectations as those at an academic institution.