As a precision, culture in the city section is for the architectural style on the map and the city view. There is no influence for bonuses and penalties.
The culture of a province (taken in account for bonuses and penalties) is in the corresponding province section, if different from the default value specified in provinces.txt.
Culture in a city section is stored in a savefile only if it is not the same as for the province.
There is no religion for a city, only for a province and stored in a savefile only if different from the default provinces.txt value.
Lastly, a savefile will always add double quotes for values that include characters (string). Double quotes are not mandatory in the DB files for single words that are keys ("tag name" of religion, culture, etc).