As I'm still working on my typeface, I'm having trouble figuring out how wide letters should be, and how the positive space affects the negative space. Obviously, our eyes determine what looks best, but is there theory behind it?

- Is there such a thing as optical rhythm? (ie: three l's "should" fit in one o.) Obviously, this doesn't work if u is the same width as n.
- Does the width of the glyph depend on the total surface area of the negative space? (ie: u should be more narrow than a) Does this apply to every character? Should this take metrics and kerning into consideration?
- Since changing the placement, width and height of the tail, arm, cross strokes, etc. affects how wide a character appears optically, should width be ignored in this case?

The reason I ask these exploratory questions is that I'm trying to determine how to maximize readability not based on how legible letterforms are, but how wide they are optically, and how they can achieve rhythm, if possible.

Thank you!