I haven't seen it mentioned yet, so I'll just say it in case no one knows or forgot. Garleans aren't a sub race of Hyur they are their own race. Technically, NPCs like Arenvald are hybrids just like Hilda. But because Garleans and Hyurs are quite close, physically, it's hard to tell them apart.

Also in regards to clans, the game, and the devs, have stated there are quite a few clans, but the differences are the same as real life variations; so minute that only the broad strokes get noticed, which are the classifications we use in game. Think about real world groupings, like Asian or Hispanic, those are very generic and contain many sub groupings. They are also two groups that can get confused for one another sometimes.

There is actually no major benefit to this, as it wouldn't change anything for your character. It would only add to your "back story", which is self-created anyway.