I've got probably the same list of what I'd term professional behavior as anyone who's been doing this more than a minute - acting in ways that others can rely on, behaving in ways that are conducive to spending a lot of time together on a team.
But that's not what we're talking about, based on OP context - we're talking about visual appearance - what someone and/or their gear looks like.
To me, yeah, appearance matters if you're going to be performing in front of others - not whether someone's skinny or overweight, or walk funny with a wooden peg leg and parrot on their shoulders, but how they carry themselves. Are they comfortable in their own skin enough to own their part of the stage? Do they look you straight in the eye? Can they present themselves as inclusive in their dealings with others? These are all things that translate on stage - things that separate those who look the part from those who don't - those who make an audience feel uncomfortable and not 100% welcome.
My secret to finding people who meet this kind of appearance metric, BTW, is simple - I try to network and work with those who work a lot. Those who get along with others generally have this part down.