Nice project. Even though some items are in a language I do not understand, the sketch provided me with a better understanding of the MySensors work. Thank you for making the connection of what I know and what I was having trouble understanding.
Quick Range Check on the WIO-E5-LE. The LE version uses only the low power PA, +14dBm max. Using the default settings except for 915MHz
#define MY_SX126x_FREQUENCY (SX126x_915MHZ)
#define MY_SX126x_LORA_SF LORA_SF7
#define MY_SX126x_LORA_BW LORA_BW_125
#define MY_SX126x_LORA_CR LORA_CR_4_5
I get about 190 meter range, just walking around the neighborhood, line of site except for some trees and power lines.
No tuning on the antenna. Just using a 77.9mm wire.
Not as dramatic as some have achieved with LoRa radio's, but plenty good enough for my house and yard : )