Hi have Full Fibre 900 FTTP and recently purchase a Netgear Nighthawk RAX200. When I set it up directly connected to the bt openreach modem it gets between 430 and 550Mbps on its internal Speedtest (this is speed to the router so wireless connection is not a factor)
When I use it in AP mode connected to the LAN port of the home hub 2 I can get up to 828Mbps.
using it in this way stops you using some of the features. I have raised cases with Netgear to said speak to BT and BT said speak to Netgear.
No idea why Netgear think it is a BT problem, it is clearly Netgear problem.