How to calculate if I need to buffer the input to my ADC?
The datasheet for the ACS70331 says it can drive 100pF and maintain stability. But in order to maintain the 1Mhz bandwidth, the capacitive load can be no greater than 50pF. The sampling capacitor for the LTC2373 is 75pF.
You can run it without a voltage follower and be fine. But since you want to maintain the 1Mhz bandwidth, you will need to use a voltage follower.