The maximum data rate we can achieve in CYRF6936 is 1Mbps using GFSK (Gaussian Frequency Shift Keying). GFSK is a modulation scheme that sends the raw data as such. It does not encode data bits with chips. So the data raw data rate remains 1Mbps.
If we use DSSS (Discrete Sequence Spread Spectrum), it uses 64 or 32 chip codes (which means 64 or 32 bits) to transmit one bit. So if we use 64 chips instead of one bit the maximum data rate you can obtain is 125 kbps. If we try to send 32 chips instead of one bit the data rate becomes 250kbps. The product (chips * data rate) remains constant.
We also have single data rate (SDR) and Double data rate (DDR) modes which give even more combinations for selecting data rates.
Note: The power level is independent of the data rate and the maximum we can obtain is 4dbm using CyRF6936.