Double Nat issue for Xbox One

> Do you think I need to change the IP adress of the X6 if the router
> that Comcast gave me uses the 10.0.0.1 format?

   Yes.  They must both be on the same sub-network.  Ideally, you'd give
the R8000 an address which is not in the DHCP pool of the main router.
(You don't want the main router handing out that address to someone else
after the next power failure.)  It ought to be possible to arrange a
reserved address for the R8000 on the main router, but it may be
safer/simpler to give the R8000 a static address.

   I know nothing about the (unspecified) Comcast-supplied modem+router,
so I don't know what its DHCP pool range is now.  Netgear tends to give
practically everything to its DHCP server, ".2" - ".254".  My usual
suggestion in that case would be to shrink the pool to, say, ".2" -
".199", and put the WAP at, say, ".200" or ".250".  Something memorable,
but outside the pool.  I'd probably pick "10.0.0.200", but the exact
address doesn't matter much, so long as the other criteria are met.

>  And will the 2 be compatible in AP mode?

   Should be.  The R8000 will be a stupid WAP, so, so long as it's on
the same subnet as the main router, with a non-duplicate IP address,
what could go wrong?  (Only one way to find out.)