only able to get 300Mb/sec with Xfinifty Gigabit

I recently upgraded to Xfinifty Gigabit, but am only seeing ~300Mb/s when directly connected to my modem.

I have a new ARRIS SURFboard SB8200 DOCSIS 3.1 Gigabit Cable Modem

I have this connected into Google Mesh - with 8 AP's throughout the house.

Overwifi I'm only seeing 60-70 MB/s...  When I'm directly connected into the modem I see roughly 300 MB/s.

It should not be this complex, so I feel I'm missing a setting somewhere.  Any suggestions on what else I should be checking as I called Comcast again today and they let me know I was a Gig speed..

Do I need to upgrade my coaxial cable to something different?

Thanks for any/all suggestions!

Kurt