BQ76952: Can the current measurement accuracy down to 1mA or uA ?

This ultimately depends on the value of the sense resistor used.  The coulomb counter generates 24-bit data natively (the raw 24-bit data is available for readout), although the processed data that uses the gain and offset values to convert from ADC codes to current values is provided in 16-bit format.  The reported current value calculated after this processing can be provided with LSBs of either 100uA, 1mA, 10mA, or 100mA. This is set using the Settings:Configuration:DA Configuration[USER_AMPS_1:USER_AMPS_0] configuration bits.

The larger values are mainly for systems where the maximum current is very high.  For example, if the LSB is 10mA, the reported current is limited to -327.68A to +327.67A, so if the maximum current in a system will be 350A, then the 100mA LSB setting should be selected.

Using the 1mA LSB size allows reporting of currents between -32.768A to  +32.767A.  Using the 100uA LSB size allows reporting of currents between -3.2768A to +3.2767A.

You can also use as large of a sense resistor value as possible, which allows better resolution.  If your system uses a very low maximum current, such as 100mA maximum, you can consider using a sense resistor as large as 100mOhm.  In 16-bit format, the LSB size of the voltage measurement across the sense resistor is 7.6uV, so the 100mOhm sense resistor would provide a measured current down to 76uA.