Welcome to AFF ... yes a bit of catching up to do, but as far as CBA is concerned ... I have one (two, actually - personal and business) and its not one of the better ones, but it goes with my other banking. I think there is basically the option to lock in Qantas points up front or convert to Virgin on an ad-hoc basis. I do the latter, as I earn QFF by other means and I have other QFF earning cards. Then, I mostly convert Velocity points to Singapore Airlines KrisFlyer miles. Its a bit inefficient (ie loss in conversion), but good for a stock of KrisFlyer miles to plug holes in other Award itineraries.
As for AMEX; what type of AMEX card do you have? I haven't had an AMEX for a couple of years but when I did I regarded it as a good 'warehouse' for points - they could stay there until I had a need to fly somewhere and then i converted the amount I needed to the airline of choice, and I still think that's a good strategy
except until the card company devalues conversion rates, as has been happening a bit recently.
So if you are not on top of devaluations, that's something to understand ASAP, although for some its too late of course.
Also read up here on earning credit card bonuses. '00,000s of points available for a little bit of sensible card churning.