Hi. Overwatch League (OWL) is a worldwide league featuring 12 teams from across the united states and 3 other countries. The organizations bought their way into the league and thus could keep their players from that team. This is why you see Florida Mayhem consisting of Misfits, Dallas with Envyus, and Seoul with Lunatic-Hai and so on. Before November, teams could pick up free agent players, such as SoOn, Unkoe, Sinatraa, Jake, Seagull etc. They can have a max of 12 players per team. There is a mid-season signing window, so players that didn't get a contract before the signing window ended now will have another shot. Players like Akm, Knoxx, FCTFTN, etc. The league works a lot like soccer if you are familiar with that format. The best players go on the best teams. I am not European so I do not know this for sure, but a lot of countries in Europe have people who can speak near fluent English, so communication is not that much of a problem, as for South Korea- the best case of it I can think of is KariV and FaTe for Immortals (Now LA Valiant). They spoke no English when they came to the states, and from what I've seen from streams, they both can speak good enough English to communicate with their team.
Contenders is kind of in a strange spot. It's probably going to be a minor league type of deal where players can try and show that they are OWL material. The top orgs are now in OWL or disbanded, so this might be a strange situation of some of the best teams not in OWL forming. I really hope this helps!