I'm running kp53 and CSSU stable; I can go with usual installation reported on post #1 to install CSSU-thumb?

My current enabled repos are:
- Nokia SSU mirror
- Nokia Apps mirror
- Maemo extras-testing
- CSSU-stable

Should I enable only CSSU-thumb or do I need to enable CSSU-testing too?
There is some known issues with non thumb-packages?
If I mess my system, reflashing rootfs should be fine, or do I need to back-up something?

Thank you very much