There are only two RF Date rates, 9600 and 115.2kbps. The default rate of 115.2kbps is the preferred rate for the two radios talking to each other for the shorter distances. If one needs to communicate over very long distances (over 20mi), then the slower 9600 RF data rate is recommended.
As for the Serial data rate, that rate should be set to what ever rate your devices require.