For inline sensing the required sampling frequency is related to the fidelity with which you want to sample the current waveform. This waveform’s frequency depends on the commutation frequency, which in turn depends on the speed you’re going and the pole pairs of your motor.
On the other hand, current sensing is also often used to implement over-current protection. Here the required bandwidth is determined by the dI/dt you want to be able to detect and protect against. Basically for the protection function the sensor should have infinite bandwidth…
Sampling the waveform isn’t such a challenge in inline sensing. For example, the commutation frequency for a 11PP motor at 1000rad/s is around 1.75kHz if I calculated that right. So sampling this with high fidelity is well within the capability of most ADCs.
Low-side sensing is another story, as the sampling has to happen in a very short time window…
Overcurrent protection is more difficult, and is generally implemented with hardware comparators in the designs I’ve seen (or built into the driver), as the reaction time of the MCU via the ADC is too slow.
AFAICT the only drivers you can get are either expensive ones from ODrive or Texas Instruments etc, or cheap ones on AliExpress. Things like this: