The adverb utterly likes to exaggerate and embellish, especially when it comes to painting a negative picture. You're likely to find utterly modifying low adjectives such as destroyed, ridiculous, and useless. Totally, on the other hand, prefers to spend its time as a verbal cheerleader: I totally agree; we totally understand!
When referring to slight differences or distinctions, the words subtlety and nuance are very close synonyms! A subtlety is a fine-grain distinction. The word nuance comes from the French word meaning “shade” or “hue,” and is used to discuss slight shades of difference in expression and meaning as well as in color and tone. There is a degree of elusiveness suggested by this term: just as it might be difficult to pinpoint the exact point at which a color in a rainbow changes from one to the next, so the nuances in a person’s tone might be difficult to demarcate or distinguish.
Someone who is composed is calm and collected—they have their feelings under control in a given moment. Someone who is unflappable is utterly unshakable or imperturbable, especially in a crisis. Someone with an unflappable demeanor, for instance, is remarkable for their even-keeled conduct and deportment, even when it might seem perfectly reasonable to the rest of us to make a flap!