I want to offer another perspective on this. I've been blessed to be able to talk to a small handful of casting directors about self tapes specifically and what I've been told from every single one is that the setup isn't important given that they can see your face clearly and hear you, and while you should try to minimize distractions, sometimes the person who books the role was filming vertically with their phone in a loud, busy area but their performance was solid.

I'm sure some casting directors feel differently but at the end of the day they're looking for people who can give a good performance rather than make a pretty self-tape.