Here's my two cents. I usually write a cover letter when applying for jobs and expect one when interviewing. As once a recruiter told me, think of cover letter as an extended resume and mention those points that you think are worth elaborating.

Instead of writing a long email, turn it into a document (cover letter) and talk about your skills (add github link) and what makes you passionate about the job. I keep it formal but not to an extend where it wastes my time.