Usually such ADC stream is processed on FPGA. You can do frequency shift, apply CIC and compensation FIR filter with decimation in order to reduce sample rate and then transfer it to MCU at lower sample rate for further processing. This way is used for realtime continuous stream processing, for example in radio receivers, radars, etc.
But if you're needs to process full bandwidth, then you're needs to attach RAM to FPGA and record sample to the RAM at full ADC speed and then read it with MCU and process it at lower speed. This is how digital oscilloscopes working.
I'm afraid there is no MCU which can do DSP for a stream at 100-200 MS/s speed.
Modern PC can do realtime processing for such fast streams, but there is another problem - to deliver that stream to CPU internal bus, which is also needs to use FPGA.
FT2232HL allows to deliver fast stream from 8-bit parallel bus to PC through USB, but it's speed is limited with 480 MBps, which is not enough to deliver digitized 20 MHz signal.