A digital servo will work with any receiver that has sufficient BEC voltage. If you are worried about low BEC voltage, get an FET servo and feed it power straight from your battery pack.
High speed radios refer to the speed with which the remote control takes your input from the wheel and throttle, converts it into a radio signal, sends it to the receiver and the receiver decodes the signal and sends the appropriate analog signal to the servo and/or speed controller.
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