Here are answers to your comments/questions (in-line):
We assume that you mean the RB-Drt-03. You can find more information in the manufacturer’s manual. More specifically, you may want to look at the examples.
They seem to have used external libraries to do various things (including a LoRa gateway) under various OS (Raspbian, Windows 10 IoT Core).
You can use LoRa modules directly without a gateway.
No, it is not if all you want is two connect two LoRa modules by wireless means.
Do you still need help setting up the LoRa/GPS hat? Are you wanting info on the Dragino loRa/GPS Hat? I have one up and running on the 915MHz band. Lots of contradictory, incorrect or misleading information out there. I also have two nodes connecting to it. An Arduino Uno with a Dragino lora shield and an esp8266 with an RF96 lora module . Both are working well.