Using different languages

Putting the question here since it is going to make the most sense: from what I can see it supports all / most unicode characters for things with accents, umlauts, etc or are there limitations?

Also there is an option to choose to preserve accents or lowercase – but why or? I assume f.e. german umlauts are considered accents, meaning if I have umlauts, I cannot have also a differentiaon of lowercase? [I dont need that, I just wondered about that selection, for me the lowercase thing should be a normal yes no in addition to the preserve accents)