I have a lot of ip cameras connected and they sometimes drop out. BT said this was happening as I have too many devices connected.
I was hoping that the Asus would help with this. Do you think that it might?
I think you have been told a load of flannel. How many devices did the BT person say is the maximum that the BT Smarthub can handle. I have at least 15 devices connected at any one time.
A "normal" router can in theory handle up to 250 devices. Obviously if the devices are wired into the router without any additional Ethernet switches or ports the wire connected devices can only be the same as the number of Ethernet Ports. The rest being on wireless connections.
Hmm, I wonder what a lot is when it comes to IP cameras and are these constantly transmitting or is it just on detection/demand? With the Asus router in AP mode (definitely the easiest option) you'd actually use the WAN port on the new router to connect to a LAN port on the BT hub. If you feel you need the extra WiFi bandwidth make sure the two routers are a minimum of 2-3 meters apart. If you can then set up the SSID/pass on the new router to mimic the hub, but set each router on none overlapping WiFi channels it'll give you the most available bandwidth with the least interference.
We've currently 29x2.4GHz devices and 10x5GHz devices connected to an Asus GT-AX6000 and RP-AX58 for a couple of devices in a service cupboard, along with another 30 ish devices on 433/866MHz connected to hubs. The previous RT-AC86u router here had been struggling for quite a while with the number of devices on the 2.4GHz band.
It's probably worth pointing out that you can see design philosophy changes in routers as you move up the scale of those that are expected to perform better. So the RT-AX59U would probably not have been my router/device of choice for your goal!
Whatever else you do, ensure the RT-AX59u only uses WPA2 WiFi security a mixed WPA2/WPA3 environment is just asking for trouble!