LQFP vs WLCSP a question about package methods
WCLSP -&gt; Wafer Scale Chip Scale Package

This is advanced packaging method, which makes the PCB connections directly on the uncut wafer. In other methods, the wafer is cut into die and then the connections are made with bondwires or through an interposer. The main advantage is reduced inductance, so higher speeds are acheivable. Additionally, the package size is reduced. The &quot;pins&quot; are small solder blobs on the bottom, so it is impossible to solder or rework by hand - you need a reflow oven, and very good test methodology. Given the level you are at, avoid this package!
LQFP - Low profile quad flat package

The pins are brought out to the four edges. Reasonably easy to solder by hand, with a bit of experience.
You should choose your package only after you've determined the functionality you need. You should also consider the effort in developing and debugging your whole circuit. For example, you might buy the required microcontroller in a big, easily reworked package for development, as you'll definitely make some mistakes, need to re-route etc. Then, if required by your application, you could go to a smaller package.
The number of pins refers to how many externals inputs/outputs are available for your use. Tip: get more pins than you think you need for development. It's much easier to downsize later, than to write code to multiplex pins etc when you just want to write your code.
For your use case, really any package type will do fine (as long as you can solder it) - it's unlikely to the largest/heaviest part of your rocket.