Verticle Script and Roman are popular.
Which 2 or 3 letters are involved sometimes help decide which style. Some shapes/font styles of the same letter(s) can fill the space better than another.
Some artistic license in drawing the letters comes in to play often, especially with the Script styles. Adding elongated loops and swirls to fill space and, tie in and overlap elements to better balance and fill the space. sometimes these get confusing to look at and even unreadable for most.
Borders are often included both for looks and interacting with the lettering itself.
