If you're coming from KEIL/IAR with FreeRTOS, RT-Thread Studio may feel a bit different at first since it's Eclipse-based, but the workflow becomes easier once you get used to the project structure.
For the Allwinner T113-S3, there are some reference BSPs and example projects available in the official RT-Thread repositories. You might find this helpful as a starting point:
https://github.com/RT-Thread/rt-thread geometry dash lite