Oooh. This is a good question and probably relevant to a lot of people, especially since the new year is around the corner and more people are looking for new roles. You're right — there are a lot of differing opinions on what you should or should not do in the job search and sometimes it's hard to decipher which is which.
In my personal experience, I have generally found following the standard formula of: application, resume and cover letter works. Different hiring managers look for different things. Some really care for cover letters, others don't. You'll probably be on the safe side if you just go ahead and include one. I think a lot of job seekers get bogged down with cover letters because let's be real: it takes time to write them and it can feel a little tedious.
I'll tell you one thing that cover letters are great for is giving context! It's a great place to show off your personality and work habits, and to explain things that can't easily be spelled out in a resume. For example, if you're in Kansas but applying to a job in NYC, a cover letter would be a great place to outline that you have family and friends in NYC and are looking to move within the next month. It gives additional context that the resume could not.
Hope this helps somewhat! Keep us posted on your search. :-)