One of the many feedback we got in the early days of RUI3 is the huge amount of memory it uses specially on RAK3172.
Because of this, the RUI3 team segmented the features in the firmware so it will only add what you need. For example, if you use LoRa P2P for your custom LoRa application, you won’t need LoRaWAN for that. So why compile the whole package if you will not use LoRaWAN?
On v4.1.0, you will be able to disable the feature you do not need and optimize the memory footprint of RUI3.
As for estimate memory use, here’s the estimated break down.
Using this flexibility will allow you to have more space for your IoT application.