You can programmatically create configurations. For example, please refer to the 421__MarketPrice__ProgrammaticConfig example.
To disable EMA log file, you need to set LoggerType to 1 (LoggerType::StdoutEnum) and LoggerSeverity to 4 (Severity::NoLogMsgEnum).
innerMap.addKeyAscii( "Logger_1", MapEntry::AddEnum, ElementList() .addEnum( "LoggerType", 1 ) .addAscii( "FileName", "logFile" ) .addEnum( "LoggerSeverity", 4 ).complete() ).complete();
However, the configurations can't be changed after they are used to create an OMMConsumer.
OmmConsumer consumer( OmmConsumerConfig().config( configMap ) );