FromTheRail
Welcome to Aussie
Is Perth permanent or just for a few years ?

AA has lowish miles needed for redemptions compared to QF / BA, and very little in cash co pay (YQ fuel surcharge). But check cash co pay carefully
You can get miles credited to an airline FFP while flying another (partner) airline, subject to rules of your program. Same with redemptions. Can use partner airlines

For upgrades the general rule is you can only upgrade a flight marketed (flight number) and operated (metal) by the airline of your freq flyer programme (no codeshares). All subject to the t&c's of your FFP and your paid ticket. Low cost tickets are often not eligable for upgrades. However as is the way with FFP's there are some (expensive) upgrade exceptions with AA/BA/IB with higher priced economy fares.

QF upgrades are not confirmed until soon before the flight (a lottery).
How QR will do miles upgrades when it joins OneWorld later this month is a mystery to me