While browsing all off the OpenWrt firmware on the website, I found this ASUS AC1900, with a github link that has tp-link in the name.
There is a sticker on the bottom that says Model: Archer A8 Ver: 1.6, however the system menu under the advanced settings it says its hardware version 1.0.
Is this ASUS AC1900 firmware the right fimrware to install? If its not, than what OpenWrt firmware can I install on it?
No, this is an entirely different device (Asus is a different brand; the TP-link one is the TGR1900 -- not part of the Archer product line.) The Onhub devices were a Google collaboration with Asus and TP-Link. The Archer series form TP-Link is not the same.
None. There is no OpenWrt firmware for your device.