June
I currently have a 300Mbps fibre connection, and the devices are Nokia ONT for fibre connection and T3200M as the WIFI router. And because I am using my WIFI mesh system, T3200m is the only a DHCP server I don't need. Can I upgrade them to an NAH 20A?
July
I don't know if they'll give out NAHs for 300mbps connections. They're more common on gigabit+ connections.
Having the ONT would be more beneficial in this case. If you don't have Optik TV, you can just remove the T3200 from the network and plug the WAN/Internet port on your mesh router into the ONT itself. Just keep the T3200 somewhere nearby for troubleshooting connection issues if they arise.