I apologize for asking simple/basic questions, but I have been out of the game for a bit and need some help.

I had an old pi that I installed retropie on and installed a bunch roms I had gotten from years back.  It worked ok.  Fast forward a few years and I found out about all these frontends and awesome interfaces and I wanted to build a new pi system with the nes case.

So I have a new pi 3+ and the nespi+ case.  I want to download and install an image.  I was looking at the 64 gig attract one (hyperspin).  I know nothing about using mega or nbz.  So just to test I am downloading one of the images on torrent (10-13hrs). So that's the background now my questions

Questions:

Anyone have personal pref on 64gb images (I mostly want to play the nintendo and sega systems)

How do I use mega or nbz files for free?

Once I get the image downloaded how do I install it on the sd card? Extract? Drag and drop?

Is there any special set up suggestions?

Also I plan to use 2 bluetooth ps4 controllers.  That shouldn't be an issue should it?

Thanks in advance for guiding me through this.