As Gardyloo said, it depends on what you're trying to get out of your backup program.

I use AA mainly, then send excess to CX. This works for me because any AA fare classes Q and above earn 100% on CX and getting mid-tier will give me free lounge access on domestic trips in the US. And not just Admiral's Clubs, but any OW lounges.

And the long oneworld award redemptions are very reasonable through CX.

So, it really depends on what you're trying to get out of the second program.

Oh also for QF/BA, I think they have an own-metal segment minimum (4?), that they enforce, unlike AA and CX. Consider those restrictions as well.

And oh yeah - welcome to FT!