Arzawa seems quite mysterious to me. It doesn't seem like there is a specifically Arzawan site excavated (yet). Do we know if they were Luwian, Greek, precursors to the Lydians and Carians, or what?
There's always more to be said on the subject, but I wrote a summary of the Bronze Age history of western Anatolia in Was Ancient Troy based in a dim memory of a Luwian Confederation?
Our knowledge of the ethnic composition of Bronze Age western Anatolia is still quite limited, as I touched on here. There have been a few surveys and excavations in the region, but there is a lot of work to be done, as I discussed in this post.