Setting the Modem Option in RHF76-052DM in Seeeduino LoRaWAN W/ GPS


I am using two Seeeduino LoRaWAN W/ GPS boards for Point-to-Point LoRa experiments.
I implmented the P2P Sending and Receiving example shown in the following:

However, I would like to know how to select the modem type in RHF76-052DM (LoRa or FSK)? how to know which one is set by defautl? I read in the RHF76-052DM datasheet that it uses Semtech’s SX1276 Transceiver. I want to disable the Automatic Gain Control used in FSK modem (found that it can be done by setting the variable AgcAutoOn to zero in the RegRxConfiguration). The ference document I used is: Wireless Sensing & Timing, SX1276/77/78/79 - 137 MHz to 1020 MHz Low Power Long Range Transceiver”, Semtech Coporation, Rev. 4, March 2015

I need to know to select a certain modem (LoRa or FSK) using Arduino IDE commands. Arduino IDE allows us to write high-level programs and I am not sure if/how I can set individual bits of a AgcAutoOn register/variable?

Much appreciated,