So I have my 2ds, running a9lh and luma. I want to change my NNID, is this possible as this without affecting the system, it is only my test NNID that is on it and not my actual one.
You really did not need to make a new thread .. People were already answering to you on your existing thread.
For your information, at this very moment, there is nothing that can get rid of A9LH short of uninstalling it yourself. Formatting or updating the system will not remove it. So formatting is safe. After format however, you must inject FBI into H&S again to install FBI and all subsequent CIA files.