Unfortunately there are no short cut in this. I doubt anyone would be able to answer your queries with 100% accuracy.
In Australia (at least), it can be generally agreed that Qantas points and Velocity points are the easiest to accumulate due to their many partners. Similarly to real world currencies (cash), an over supply of any currency would encourage devaluation. Hence, it will require more of the devalued currency to exchange it for a product/service.
Personally, I would suggest that you stick to QFF if all you are trying to do is accelerate your points earning to be able to get sufficient points for your planned trip. However, bear in mind that if you collect solely QFF pts, your options of flights are limited to Qantas partner airlines. If you are not flexible and leave booking to much closer to departure date, you will potentially find it is rather challenging to find reward seats still available. This is another effect of a popular FF program-> there are many more people with higher FF status and balance out there competing for the same seats. There are pros and cons to every frequent flyer program and credit card.
Please also keep in mind that Qantas and Cathay Pacific (Asia Miles) are both oneWorld airlines. i.e. you could use Qantas pts to redeem Cathay flights and vice versa.
I hope I have at least clarified some of your queries.
Personally, I have balances in multiple FF programs and some flexible points to increase my options available to get me award/reward seats from A to B. The downside to this is that I have too many options at times. This makes decision making more challenging. #firstworldproblem I know. However, I too struggle with finding seats for last minute flights and peak periods too.
Signup bonuses is a large part of how I collect my points. However, please be cautious towards the effect you can do to your credit rating.
My last piece of advice is: Just start with Qantas and adjust your strategy as you slowly learn more about the point game and as more changes come to make our point hacking more challenging. Better to start somewhere than being paralyzed by over analysis.