I host a Matrix server for my family and we regular make audio calls to Australia. I had to try a few services before I found a $5 VPS that worked well, but network was always the limiting factor rather than server specs. The unavoidable latency makes video calls unpleasant so I can’t speak to that.
Have you tried using Mumble [1] to chat with your family? I ask because I have chatted with gamers that are in AU and NZ from the US with almost no detectable latency. I can see their latency in the client, but I can't hear it. There are open servers you can test it out with to avoid setting up the server and save you some time setting up the server in the event it does not work better.
I ended up at Genesis Hosting. Their web console is a little rough but the server specs and network performance are better than any other $5 VPS I’ve tried.
