This feels like you're asking us to answer a homework question, lol
But that aside, it can be difficult to say as there's quite a few variables and it almost surely varies industry to industry. On top of that, any given answer here probably doesn't have intimate insider knowledge of every industry, but just a small handful they've been in for years.
For example, I shoot a lot of Real Estate. Self Expression doesn't really come into play much, although having a style that broadly appeals to multiple clientele does. And that just brings up the question of what the actual difference is between self expression and the style you've formed over years of shooting. I've had multiple realtors explain to me what they like about my images versus other photographers, and often it comes down to my capturing large areas well, and frequently, compared to other photographers narrowing down and capturing smaller segments of larger open rooms. Is that self expression? Or more style? And what's the difference?
Maybe not a good question for Real Estate Photography, but how about Weddings? Or fashion? Weddings as a current cultural phenomenon value self expression more, and Fashion Trends even MORE so. I've shot over 100 weddings at this point and know that, because weddings are more personal and people are a bit more picky, clientele who chose me definitely did it because of my style and personality. Is that a product of self expression? Again, hard to say.
My take is that cultivating "Self Expression" is maybe missing the point. Or a misunderstanding of what's actually going on in the creative. Much more important is having a clear creative vision and a plan for bringing it to fruition. In movie directors, you tend to see styles come out and I think those styles are a product of strong directors having a vision for what they want and how to achieve it. Whether it's "Self Expression" is neither here nor there, and I think is kind of unimportant.
...Although I wonder how I'd agree or disagree with this take back in my teen years, where self-expression seemed much more important to me and my peers.