Thank you for the link. Yes, my settings match those recommendations.
I do have other devices connecting to my router using ac so it shouldn't be a router issue.
Yes, Windows 10. I just got the latest update yesterday. No change to wifi performance. I am concurrently discussing with Asus regarding this issue. They have not recommended a different driver, just recommended I use the latest available driver.
I have fixed the issue by enabling QoS and WMM on my router. Not sure which setting made the difference, but I suspect it is the QoS.
Thank you for working with me on this issue.