I read a Japanese book that boasts itself as a textbook for men's fashion. It's titled, "Quickest way to look fashionable" (最速でおしゃれに見せる方法), published on 9/17/2015.
The book was very good. The author MB, who has been in fashion industry for a long time, distilled his ideas of looking fashionable and good in the street and came to theories. His basic formula for street wear is "to balance casual and formal" to look fashionable and to be likable.
A useful concept is that, he rates all components of men's clothes in a "casual-formal" axis.
Casual being casual, like sneakers, sweatpants, jeans, hoodie, t-shirts, baseball cap, etc. They tend to be relaxed and colorful.
Formal being something like serious business/dress attire; dark shiny leather shoes, dress slacks, constructed jacket and dress shirts. They tend to be structured, monotone, or black and white.
Even within an item category, there are more dressy/formal ones and more casual ones. Pale and torn jeans are more casual than dark skinny jeans.
And he advocates to mix and balance the casual components and formal components in one appearance for a street wear.
I had not come across a book that states street fashion rules in such a simple and practical manner. Most magazine photos and company catalogs have an agenda to sell and tend to focus on components themselves, not necessarily the whole appearance, and much less on how to construct the look. "Looking good" is left to some "sense" or individual's "talent" that are too elusive to grasp quickly.
He says otherwise; there are rules that can make your appearance appealing to a majority (not all) of people, and he'd teach the rules. I like this kind of thinking. To tell the truth, I wanted my "Beginning Argentine Tango" book to be like that (in the field of Tango, not fashion of course).
Consistent with his assertion, we have been told that shoes are the most important part in men's fashion. Shoes are a main component of the bottom, also are a part of "tips" of the body that tend to get attention.
We know wearing formal and sharp shoes can uplift the whole attire, and wearing overwhelmingly casual crocs sandals (these guys in the photo) can irreparably damage otherwise dressy attires. Even expensive suits cannot save the look.
If you look at street fashion photographs with this theory in mind, you'd be surprised how much of them follow his theory.
When a guy wears sneakers (casual), he may tip the balance to formal side by wearing slacks and a jacket (formal). But he might add more casual side with long sleeve t-shirts. Right. I've seen these street wear photos in some websites like The Sartorialist (link to the site).
I recommend the book (well, if you can read Japanese. Sorry).
Then, I was thought-experimenting by rating various partner dances in "casual-formal" axis.
What makes difference between this dance "casual" and "formal"? I'd say, how it looks. Specifically, how classical and line-emphasizing the dance looks. Ballet-like long lines makes it more formal, and body rolling makes it more casual. Assuming that they are all danced by the performer-level professionals, how they look and how much classical appeal they hold is the criteria.
Then, elite dances like Ballet (duet), competitive ballroom dance by professionals, stage tango, contemporary duet dance by dance company, would be formal. Among ballroom dances, smooth dances would be more formal than Latin/rhythm dances, although they both require hard training to perform well.
Casual dances would be like many social party dances. Kizomba and bachata would be most casual. Most Salsa and swing styles fall on casual, too. The less you need specific practice for the basics, the more casual the dance rating goes.
There are dances fall in between two extremes, like social style serious Tango, or contest-level WCS. Some dances hold more potential to look formal than others.
Personally, I like formal dances more, to watch and to do. I feel like, casual dances are fun to do, but they may not look as good as the dancers can. I am referring to a fact that Kizomba pros may have harder time to distinguish themselves from intermediate non-pros compared with Ballroom waltz pros, who "obviously" look different from intermediate non-pros. But you can have your own opinion on this one.