Sure,CREATOR is a open source hardware,you can do every thing ,we provide the Arduino SDK.
But if you want to use RAK473, you have to use the development board : https://www.aliexpress.com/store/product/WisNode-UART-Open-Source-Hardware-module-development-board-compatible-Arduino-AT-command-communication-and-network-configuration/2805180_32789820244.html?spm=2114.12010612.0.0.5bdadf47T56O8i, CREATOR does not support RAK473. The hardware they use is the same, but the software is different.