Hi Kuo,
1) It is suggested to use AutoTune at all times. The motor specified should work with AutoTune.
2) What do you mean RSENSE suggest how to design?
The RSENSE is the same for all decay modes. It is suggested to select a sense resistor that will create no more than .5V on the xISEN pin. For example using a 1 Ohm sense resistor will create .35V. The VREF voltage would be 2.3V.
