The normal beads give you the widest range of options for most brands. I agree with u/Gena_Official on the brands too - don’t get a no name brand if you want to have fun with this; off brands can have any number of problems (namely fusing) so it’s best to avoid them. Judging by the links you provided you’re in Canada, so you might want to give BeadsEh a look; it would be better for if you get more serious about this too.
Stick with regular Perler or Artkal for the best experience IMO. Once you get more into it you can certainly try mini, but be aware you may be missing some color options that the midi/regular size beads have - at least that’s the case currently.

Aside from that, you’ll want to learn about the tape method for ironing so you don’t warp your boards. There’s a tutorial on the Perler site, but u/kylemccoy has some fantastic videos on various ironing methods, including the tape method: https://www.youtube.com/watch?v=Hz-P-YjOK0U.
I also recommend watching him in general; really fantastic stuff and it certainly got me more hyped about beading, and I learned a ton :)
Also when ironing, make sure your iron is on medium heat! Otherwise you’ll have a bad time.

For making magnets, get yourself a hot glue gun if you don’t have one already, and pick up a pack of craft magnets to glue on. I haven’t made any keychains, but I’m sure you can find a pack of key rings for cheap too.

For placing beads, tweezers aren’t for everyone, so don’t feel bound to them. I believe Kyle McCoy just does it by hand, and others like myself use a stick type tool, such as a toothpick, or unbent paper clip. These allow you to line the stick with many beads and place a bunch down quickly. I use tweezer mostly when I’m removing beads to switch out for another color or something similar. Placing all of the beads with tweezers it too slow For me.
If the set you find doesn’t come with tweezers, here is a great set that comes with a few options to try (the basic plastic ones you get in most kits are trash, some of the ones included in the set I linked are the same type as the more expensive Perler brand ones)