Hi,
If you plan to use Yarn Spinner or Ink, please be aware that the Dialogue System currently imports Yarn 1.x format, and for Ink the Dialogue System acts as a front-end and runs the Ink Unity Integration under the hood. For all other formats (Yarn, Twine, Arcweave, articy:draft, etc.), it imports into the Dialogue System's native dialogue database format.
That's beside the point in regards to your question, since in all cases the Dialogue System manages the UI. The Dialogue System's default UI system can work with UI Text, TextMesh Pro, or SuperTextMesh. As long as your font supports characters with those diacritical marks, it will work fine. (You can also bypass the Dialogue System's default UI system and provide your own implementation of the simple IDialogueUI C# interface if you prefer to do that instead.)
Furigana may be a little more complicated. You can do it with TextMesh Pro like in
this Unity forum post. Side note: Years ago, Joe Strout, the originator of that forum thread, provided a furigana implementation for the Dialogue System's older UI system that used legacy Unity GUI. If you load up an old browser such as Internet Explorer, you can play it
here. I can try to dig up the original source if you're interested, but since it uses the older Unity GUI system I recommend using TextMesh Pro with the current UI system instead.