RTW wouldn't work because you said you want to come back to your origin city
before the end of your trip and that is usually a no no.
Better to combine it or two separate tickets if you don't want to be away for that long.
If you are not too good at jetlag I would combine it because you will be just over the jetlag in Korea and feeling good then come back to Toronto and take a week or two to get over that trip and then be off again and have to adjust to a new time again.
Whereas if you flew from Korea to Brisbane you would be ready to go once in Brisbane as it's basically the same time zone as Korea
