The link Urquhart1244 provided is excellent advice for most users. The questions is, what are you wanting to do with your router? If you simply want to protect a home network where your family is browsing the Internet, gaming, streaming video and so on, then a router's default firmware and set up, then configured according to Apple's guide, is probably more than good enough.
If you want some additional security over and above that, there are things you can do to tweak the DNS server the router defaults to away from your ISP to OpenDNS, Cloudflare or other providers who may provide blocking of malware or content filtering on their DNS offerings.
Some router manufacturers, such as eero, have partnerships with various providers and have a premium security service that also includes things like included subscriptions to 1Password and Malwarebytes (I'm sure at least some of their competition in the home mesh space have similar offerings).
And then, if you really want to go deep, there are custom firmwares such as DD-WRT, Tomato and (for the Asus line) Merlin's AsusWRT. That gives you custom control over almost the entire 802.11 stack, if you know what you are doing and need that. But honestly, most people don't. And those that do probably also need to learn how to set up a proper firewall and network DMZ...
So, what is it you are looking to do with your home network?
As far as Australia goes - basically every home networking company of note (Asus, Netgear, TP-Link, Google, eero, like all of them) sell in Australia. Any decent "best of" site, from the Wirecutter to PC Mag to Tom's Guide, will give you options worth looking at.
