Using SPI to get higher sampling rate from ADC module vs using ADC on microcontroller
You could use an &quot;Arduino&quot; compatible module such as the STM32F103C8T6-based ones, which have claimed &quot;12-bit&quot; and &quot;1us&quot; ADC peripherals. Read the datasheet with a jaundiced eye to determine the actual performance. You can't expect to match the performance of a fast external ADC from a top-line company.
I think it would be more common to use an external ADC to get better performance than the on-board 10-bit ADC.
You should think about where the data is going and whether the processor is up to handling it, beside just the raw ADC speed.
Also, you can make the ADC in the ATMega328 run 5-10x faster if you don't use the analogRead function, but allow it to free run with interrupts. Perhaps with some loss in performance.