clearModemPreset

Either modem_config or bandwidth/spreading/coding will be specified - NOT BOTH.
As a heuristic: If bandwidth is specified, do not use modem_config.
Because protobufs take ZERO space when the value is zero this works out nicely.
This value is replaced by bandwidth/spread_factor/coding_rate.
If you'd like to experiment with other options add them to MeshRadio.cpp in the device code.

.meshtastic.Config.LoRaConfig.ModemPreset modem_preset = 2;