The question should be will the Panoramic allow you to use MoCA? The next question would be do you need to increase the bandwidth upstairs?
Panoramic. If you only subscribe to Cox Internet service (no cable TV), the Panoramic will disable its MoCA feature. The Panoramic will only enable its MoCA feature if you subscribe to Cox TV service and rent the Cox wireless streaming box. I included a link from 2 years ago about Panoramic and MoCA.
The 380-400 Mbps measurement is pretty good if you have 2 devices connected to the Panoramic. A more accurate test would be to disconnect everything from the Panoramic except 1 device (PC or Xbox) and then run a test. Meaning, the Panoramic would provide all its available bandwidth to only 1 device, and then you should be measuring 760-800 Mbps.
Bandwidth. Do you need more than 380-400 Mbps upstairs? Streaming 1 UHD movie requires 25 Mbps and you'd just add whatever bandwidth the Xbox requires to simultaneously use both. Would this total be more than 380 Mbps?
To use a moca system, you would need an ethernet to moca adapter, and then something like an Actiontec WCB3000N01 for the other end. Alternatively you can use a powerline adapter liek I did, TP-Link Powerline WiFi Extender (TL-WPA7517KIT) - AV1000 Powerline Ethernet Adapter with Dual Band WiFi. I have it setup as mesh using the same SSID as my Arris 2460 AND it's got ethernet so I have wired connections on the other end as well. It runs fantastic, with almost no loss in speed when on ethernet upstairs, and the wifi does it justice.
I remembered a post from 2 years ago about Panoramic having "recently" started to disable subscribers' MoCA feature even with MoCA adapters. I found a post, read halfway through and felt it was the correct one. However, I should have read the entire post because superbigwaff details how to bypass this disabling with specifically-equipped adapters and filters.