For my setup I directly connected from the ONT to the R3.
Under WAN:
Changed the MAC address to match the Google provided gateway
Changed DNS to the best one for me (1.1.1.1 primary, 8.8.8.8 secondary)
Disabled upstream DNS
Manually keyed in MTU to 1500
Left IPv6*ENABLED* (IPv6 is a toss up on if it's better or worse to have on or off. For my fiber connection, it's proved to be better in the long term.)
LAN settings:
Left IPv6 *ENABLED* (IPv6 is a toss up on if it's better or worse to have on or off. For my fiber connection, it's proved to be better in the long term.)
UPnP enabled
Internet rules settings:
DO NOT SET ANY INTERNET RULES, DELETE ANYTHING WITHIN HERE. This broke my wifi speeds, wired speeds by literally in half.
RGB lighting settings:
Turned all off due to stability issues I have ran into with the router
Geo filter settings:
Disable steady ping
Enable geo location
Enable strict
Ping optimizer settings:
Set everything to 100%
Congestion control mode set to low latency
Speed test bypass is enabled at the moment/on/currently Red
Smartboost settings:
Turned on smartboost
Simple mode enabled
Removed all activities and devices
Adblocker settings:
Manually disabled every device in adblocker
Then turned off adblocker.
System information:
Confirm/set time zone to your timezone
Turned off all protection/protocols in troubleshooting and disabled telemetry under troubleshooting. With these exact settings I get these results consistently get 950-980 Mbps through ookla or directly through router speed test. Wireless I'm now getting 750+ Mbps and 4ms ping (when pinging the Texas Google fibers server of course