Miss Pross is a very caring woman and is like a "shadow" to Lucie, she also a proud English woman. Madame Defarge on the otherhand is also described as a shadow, meaning how she covered things in fear and darkness. She is a cold, bloodthirsty and ruthless woman, determined get her way, and is all for the French republic.
Darnay and Carton look very similar and love Lucie, but differ in personality. Darnay is a humble, hardworking man, he accepts work. Carton on the otherhand, is bipolar, at times he may work without sleep, or will not do much, he also constantly drinks and is often depressed.
France is where the revolution takes place, where everything is uneasy and unstable. Many are dying and blood is being spilled by the guillotine. England shows more stability, mostly shown where Lucie and Darnay are able to settle down in a quiet house peacefully. Here, life is quieter with more opportunity and safety.