What can the UU and UT be for a new Croats civ?

I have to said it is not simple like you stated.
Even yes, if you don’t care the ethnic classification in some degree, there is no any problem at all.

Be clearly different in my version.
There were Boyars since some Slavic people were in the Vlachia, which did not mean Vlachs were Slavs.

I had post my Bengals and Dravidians tree on the other thread.

So I said not every Europeans were Germanic there.

BTW, we are off-topic now. I still hope someone can give me feedback about Croats.