If you have understanding of how the hardware acceleration has been configured, watch this:

https://www.youtube.com/watch?v=vCZZ15fa2nU&t=1902s

If not maybe worth watching from start.

Max firewall bandwidth on 2862 is 400Mbps https://www.draytek.co.uk/products/business/vigor-2862#specifications

FTTP uses a fibre modem.

If you use your 2862 as an access point, you won't be limited to 400Mpbs, especially that you said you had switched off WAN1.