You can configure ArduinoJson with the following macros.

ARDUINOJSON_DECODE_UNICODE
Enables decoding of Unicode escape sequence (\uXXXX)
ARDUINOJSON_DEFAULT_NESTING_LIMIT
Defines the default nesting limit
ARDUINOJSON_ENABLE_ARDUINO_STRING
Controls the support of the Arduino String class
ARDUINOJSON_ENABLE_COMMENTS 🆕
Enables the support of comments in JSON input documents
ARDUINOJSON_ENABLE_NAN
Activates support of NaN in JSON documents
ARDUINOJSON_ENABLE_INFINITY
Activates support of Infinity in JSON documents
ARDUINOJSON_ENABLE_PROGMEM
Controls the support of Flash strings
ARDUINOJSON_ENABLE_STD_STREAM
Controls the support of the std::istream/std::ostream
ARDUINOJSON_ENABLE_STD_STRING
Controls the support of the std::string class
ARDUINOJSON_NEGATIVE_EXPONENTIATION_THRESHOLD
Controls the exponentiation of small floating-point values
ARDUINOJSON_POSITIVE_EXPONENTIATION_THRESHOLD
Controls the exponentiation of large floating-point values
ARDUINOJSON_USE_DOUBLE
Selects the storage type for floating-point values
ARDUINOJSON_USE_LONG_LONG
Selects the storage type for integral values