If I play through the steem platform, and my friend plays through the launcher from the site, can we meet in the world?
Yes, as long as you are playing on the same region
I can select the region from the steam, but my friend from the Launcher can't.
Then he has downloaded the game from another region, as only NAEU has the selection in the launcher. If he does not see it, he is in another region. Make sure to download the game from this NAEU website. He would need to buy the game from this website again, and start a new account on this region in order to play with you