Newbie here. I need answers!!

I started the game a few days ago and i'm having a blast. I've managed to buy a Cobra and i'm doing bounty hunt missions with some cargo transport. Next thing i want to try is laser mining and passenger missions. I think i'm doing ok but its a complex game and I have two questions:

1. I understand that the number in a module rated 2F, the "2" would be the size of the module and the "F" would be the quality of It. Right?

I've googled a good loadout for the Cobra, and a guy had two Cobra build guides:
One beginner loadout (1 mil. total value)
One "A-rated "loadout (~7 mil. value) https://www.reddit.com/r/EliteDangerous/comments/gon2og/cobra_mkiii_outfitting_guide_for_beginners/?utm_source=share&utm_medium=android_app&utm_name=androidcss&utm_term=1&utm_content=share_button

Why the A-rated build keeps using 1G pulse lasers? The other modules are A rated so why dont use 1A pulse lasers instead? (for example)

1. I need help with the scanner thing.

I see there are 3 basic scanners. The ship scanning is just pressing A (using Xbox controller) looking to the npc ship, right?

The other scanners like the discovery scanner i dont even know how to activate it. I setted them in a fire group ok, but It just says Wrong Mode or something like that.

How I activate all the scanners like the Planet scan or the belt scan looking for minerals? I mean with the controller, i know i have to install some scanner modules but how I activate them with the controller?