So I've read pages and have things in everything.
I believe mega metagross to be really needed, because he dropped from OU to almost NU.
I like Pikachu, and the speed boost I Raichu made it possible for me to use it on VGC, since it's now the fastest Fake Outer in the game.
About Japan, vgc is the game there, and they tend to meet personally more than use online forums. Their Pokemon communities are more rl than virtual.
And about 6x6 OU being better than everything else, I think it's personal. I prefer VGC, since the strategic level for doubles is higher imo, and the battles don't take forever to end. (I know we're at Smogon, but I'm not a Smogoner battler, at least not as my first option. I do battle Smogon when it's needed, but not my first)
99% there won't be. Changing clothes is a Kalos thing. If you see the secret bases, people there are supposed to be other players. Yet y they are NPCs sprites. In the original games, your character in another person's game was in NPC sprite. So I believe you can give up on this dream.