Any list or recommended tweaks for the CK64 CreationKit.ini and CreationKitPrefs.ini?
You still have to add the multiple masters line to the CreationKit.ini.
If you're going to be messing with scripts, you have to unpack the Scripts.zip file (I recommend using a mod manager for this so you can easily add and remove them), and you have to add the lines for the scripts to the to the CreationKit.ini. Mine looks like the below:
bPerforceEnabled = 0
iMinMemoryPageSize = 128
iMaxMemoryPageSize = 512
Please note that the above path for sScriptSourceFolder is not the default path. I have mine set up to match how the paths for old Skyrim. SSE changed the path in the archive for whatever reason (or they packaged it incorrectly) so the new CK can't find the script source files for any mods being ported over to SSE. Bethesda is apparently aware the the problem. I don't know if they've fix it yet. If they did, then the paths above should be correct.
That's all I've had to do to get the CK running correctly for me.