How much can you afford for housing? 1+ acre within 30km of SYD/MEL would cost >USD 2 million. Same in ADL would be a quarter the price (perhaps for good reason, though I love Adelaide I'm not sure I could live there). Your 4 choices are dramatically different, but I'm guessing you want the Gold coast.

Do you need fast internet access? Then the NBN (national broadband network) access is a big consideration, some rural areas have better/faster internet with NBN than the big cities. But it is very localized (5km away could have no internet access, worst case).

For culture, no contest, it is all in Melbourne (with a bit in Sydney). Similarly for food. Cost of housing is probably the big determinant, Rural victoria and NSW can be quite cheap (you can get a nice property for <$200k USD if you go to "undesirable" towns, mostly lacking local employment which shouldn't matter to you).

Research would pay big dividends, there are some great places to live in Oz at all price points. Good luck.