Nighthawk X6 router speed testing at 120mb/s when modem is testing 400+mb/s

We are in LA and have Spectrum internet with over 400mb/s speeds (tested and confirmed from modem). We just had an installer out that re-wired for the newer internet. Now, just days later, we are getting 120mb/s tops out of the router with confirmed 400+mb/s from the modem with speed tests (directly connected).

Any ideas on how to play with the router settings to get better results? My room is right next to the router (less than 8 feet) and I still only get 120mb/s from the router.

Thanks ahead of time!