Atlanta, GA - Speeds stuck at 320 down/7.2 up Mbps after upgrading to 800/20 service and from DOCSIS 3.0 to 3.1 modem (ARRIS S33)

Another complaint about not receiving advertised speeds. I decided to upgrade from 400 down/10 up Mbps service to 800 down/20 up Mbps. I also upgraded my modem from DOCSIS 3.0 to 3.1 (ARRIS S33 v2; Xfinity certified) to match the service. In the two weeks since upgrading, my speeds have not approached 800/20, but are close to my old 400/10 speeds. Measured speeds average 320 down/7.2 up Mbps. Xfinity online chatbot help said service is good on their end and my modem also looks good from their end. In my searching to troubleshoot, I confirmed that Atlanta, GA is one of Xfinity's Enhanced Speed Markets. I also learned that my ARRIS S33 is not certified for faster upload speeds, although it should work for the faster download speeds up to 2.33 Gbps. Again, my download speeds are not even close to the subscribed 800 Mbps. I also learned that only 4 cable modems are certified for faster upload and download speeds (none of them made by ARRIS!). So, the big questions are:

1. Do I live on the right street in Atlanta to get Enhanced Speeds?
2. If I live on the right street, am I really required to ditch my S33 for, say, a Hitron Technologies CODA56 (certified for up to 455 Mbps upload)?

I would be most grateful for any help. 👍