A cursory google reveals a complete absence of statistical attempts to devise weighted medal tables for the 2018 Commonwealth Games.
So I've done it.
I've chosen to go with a weighted medals per capita, like in this Olympic Games analysis, where a gold medal is worth four points, a silver two points, and a bronze one point.
Population metrics are from the United Nations World Population Prospects, the 2017 Revision (via Wikipedia). For Australia I've subtracted the Norfolk Island population, as they are a separate entity for the Games. For the United Kingdom, I've prorated the 2017 population into England, Scotland, Wales and Northern Ireland using earlier splits.
And after all that, the per capita winner is...
One bronze medal in lawn bowls for its 1748 people was enough to take the top spot, ahead of Nauru and the British Virgin Islands.
Australia dropped to 15th place.
Click the image to enlarge the full Per Capita table.