"Not like those in the Chinese part of the city: a jumble of rickety shops with people, vegetables, crates of quacking ducks, yard goods, bamboo baskets, and mangy dogs spilling onto a street so narrow it was hardly there." How does the word choice in the sentence affect the meaning of the text?

It adds a feeling of chaos, negativity, and discomfort to the text. It portrays the area described as undesirable.

Explanation:

These parts of the text create this mood

Rickety, or unstable,

Crates filled with quacking ducks,

Mangy dogs, spilling onto narrow streets,

taking into account that a theme is the central topic a text treats and can be developed through a story, play, poem etc. the following are themes that can be further developed:  

my best friend jeffrey has many unusual interests. (the story could be about each of the unususal interests)

once a man gives his soul over to evil, he can never go back. (this could be a saying or a proverb)

the three sheepdogs lay around the yard all day. (it could be developed detailing how each of these sheepdogs lay around)

a priest's collar has an unusual effect upon people. (it could be developed detailing the different effect upon people)

innocence is a powerful force in a world full of corruption. (it could be developed detailing how is a world full of corruption)

king lear is a play shakespeare wrote later. (it is just a sentence and doesnt give any idea or topic to be discussed in details.

evil often wears the disguise of innocence. (this could be a saying or a proverb)