I don't think WhizComms ever provided an ONT, but they've provided ONRs that can be bridged (functionally equivalent to ONTs) in the past. See above for some comments.
Your Asus TUF AX4200 wireless router has a 2.5 Gb/s Ethernet port, but the equipment WhizComms provides for their 2.5 Gb/s (fibre speed) service is limited to 1.0 Gb/s per port. You'll get that much delivered to your Asus TUF AX4200. Whether your Asus wireless router can do anything with that higher speed depends on a variety of factors including your local and ever changing wireless environment in/around your home. You can attach one or a couple wired devices to the WhizComms ONR, and they can get their own 1.0 Gb/s ports. The aggregate speed limit across the ports will be 2.5 Gb/s. Will that matter (make your life materially better, etc.)? Probably not, but it's possible.
If your WhizComms ONR is
not bridged then it's generally best to disable any routing functions in your Asus TUF AX4200 and configure it as a wireless access point (WAP).
On edit: It looks like the Asus TUF-AX4200 might
support WAN port aggregation. So you might be able to get 2.0 Gb/s (1.0 Gb/s+1.0 Gb/s) into your Asus equipment using 2 cables. Whether the Asus TUF-AX4200 can deliver any
real-world benefits to your wireless devices with that configuration is a separate question.