I am not sure. I've read that the Qiang are related to Tibetan tribes, and I've read that they were also different as well. The Qiang were living in both the regions inside and outside of the Tibetan Plateau. So maybe they may have been just "one" of the proto-Tibetan peoples.
Today, the Qiang are classified as their own ethnic group and live in Sichuan (Shu-Han territory) as opposed to also the territories of Xiliang (Ma Teng/Han Sui in the 3K map). They apparently have a matrilineal culture with tower-pyramid like fortified towns and castles, so they seem to have a different culture and architecture from Tibetans in the Tibetan Plateau.
I think so. They would've been more around Central Asia and the Western Regions of the Han Dynasty. So they could be relevant if they were still interacting or attacking the Han commanderies and military governors of the Western Regions (later taken over by Wei I believe), or we can use a little TW fiction and say the Northern Xiongnu were still attacking further east as well.