I'm reference UG-364_User Guide to build code Base on RFB =750 ohm, Z= 680ohm to measure Correct Impedance,

Below is my configuration!

Question1 : When MCLK=1MHZ, how about sample rate & DFT Value?

Question2 : MCLK =16MHZ,RFB =750 ohm, Z= 680ohm, Read data of Impedance is 1k~400 ohm, is that Correct?

Question1: Sampling frequency = MCLK/16 (p. 20 of the UG-364 User Guide you are referencing), so 62.5 KHz. If by "DFT value" you mean resolution at coherent sampling, then it scales with MCLK and at MCLK 1 MHz it is about 61 Hz (p. 19 of the UG-364 User Guide you are referencing).

Question 2: If I got it right, the "Read data of Impedance" is ∞ - 680 ohm.

Note: RFB is not the same as R2 on the software screen, R1 is your calibration resistor that is replaced by Z when performing measurements.R1 value needs to be typed into the "resistor value R1" cell when calibrating by pushing "Calculate Gain Factor" button.