I recommend working this out in reverse and start with figuring out redemptions before you worry about earning.

At least spitball a few trips you want to take, do some mock award bookings to see what kinds of points it will take, then work backwards to see if there are cards that make sense to help you get points into those loyalty programs.

When you play the points game you are earning a currency that is not cash. It can be substantially more valuable or less valuable depending on your travel goals, ability to earn points, travel flexibility, your home airport/available airlines, etc.

Redemptions are the hard part, and that includes having to know yourself and how many hoops you're willing to jump through to chase "maximum value." Once you figure that out, the method of earning is much easier to solve.