Sorry. I assumed because I quoted a section, it would be clear that I'm asking about the section I quoted. That's on me.
So:
1. What's this about two notoriously large and bad groups for the EU region? I've somehow never heard of this before now.
2. I was under the impression, based on something
@Dessgeega said around the last North American Splatfest, that Splatfests were locked to the copy of the game you play. So having the EU version of the game means you're locked into the European Splatfests, but not locked out of Splatfests overall. This could be an issue for some or not, depending on if real life friends play Splatoon or not, but it may also be a negligible difference on a case-by-case basis. Of course, it's always possible that I'm wrong about this as I am often wrong.
I hope this gives you the clarity you seek. I'm mostly interested in finding out about that first point if you are willing to elaborate.