I just ran below three blocks and monitored the AT commands they would send to the modem (w/o the modem actually stacked / connected to the M5Stack):

GNSS power control 'on' -> AT+CGNSPWR=1
GNSS work mode 'GLONASS' -> AT+CGNSMOD=1,1,0,0,0
GNSS NMEA poll task -> AT+CGNSINF

This means that the AT command AT+SGNSCFG=<MODE> I mentioned before is not part of these three blocks.

BTW: checking the work mode on my SIM7080 for the first time returns:

AT+CGNSMOD?
+CGNSMOD: 1,1,0,0,0

which means GPS and GLONASS are enabled. And since this command's parameter saving mode is AUTO_SAVE_REBOOT I would assume that this is the default.

In other words if you omit the work mode block I'd assume GPS and GLONASS are enabled by default.

Thanks
Felix

I think you can choose any of the four options as GPS is always included by default. From the SIM7080 AT command document:

AT+SGNSCFG="MODE",<mode>
0 start GPS and GLONASS constellation
1 start GPS and GALILEO constellation
2 start GPS and BEIDOU constellation
3 start GPS and QZSS constellation

Thanks
Felix