Hi from sydney welcome to the board heaps of info here and a few resident GUE instructors. Liam is the instructor in australia his shop is
dive centre bondi
I think most bp's are the same only wieght ss or alu is diff but as for wings u want the right one for the job wich means a smallish 30lb for singles and larger for doubles. I wouldn't try to use one for both. I haven't used Dive rite but am very happy with a haylcon eclipse single and old style explorer 40lb for twins. They are a really simple design inflator and one rear pull dump.
Both of mine have had a lot of use only thing i have done to them is pull apart inflator occasionally and fill with lube.
good luck i think there is a pretty sizable dir community in melb if u need help with anything