@Kevin_Z, thanks for your response. I've actually been working with TP-Link support since I posted this. In short, yes I've ensured the routers are using different 5GHz channels and are both running...

I have two ArcherC1900 v1 units with the new one connected to the old one via LAN cable. The new one has similar performance on the 2.4GHz band as the old one but for the 5GHz band it seems to...