QSSI and UM architecture

IoT Modules Smart Module
,
1

I have a SC200E smart module. and its AOSP source code contains QSSI.12 and UM.9.15 folders. they both have similar directories in them. like device, packages,vendor etc. which one should i should work on. for example. if i want to add a splash screen, there are package folder in both (QSSI and UM) folders.

2

Dear, customer:
In general, you can modify the files in QSS folder.

Thanks