Suffice to say that the theme (the WHAT of the movie) is going to determine the style (the HOW of the movie).
Good style, to me, is unseen style.
It's art. It's commerce. It's heartbreaking and it's fun. It's a great way to live.
If I don't have a script I adore, I do one I like. If I don't have one I like, I do one that has an actor I like or that presents some technical challenge.
There's no such thing as a small part. There are just small actors.
The varying physical characteristics of the actors may also necessitate changes. Sean Connery is six feet four. Dustin Hoffman isn't.