You are close. they are instanced areas on the map, however, the instances are still on the same server. So it isn't 4 people per instance, it is 4 people per entire map server.
Yep, pretty much this! It's easiest to just think about it as 4 players per server. 😊
Does that mean we have to fill up our parties before entering the game or does our character create its own server so friends are able to join at will
It depends on what you want to do...
When you launch on a mission the game will look for other people who are also launching that mission for the first time and try to form a group with those folks. If everything works out, you'll matchmake with some folks who are doing it for the first time.
If there are empty spots in your group, the game will automatically let your friends know that there's an opportunity for them to join you - and they can hop in and help you out.
Beyond that, other players can queue up to help out newer players using the reinforcement system. They can matchmake in and help round out a group.
If you prefer to play with just your friends though, you can always set the game to private and make your own squad.
For Freeplay, you'll generally be matchmade into an existing server (new ones are being spun up and down all the time). There will likely be other players on that server 😊.
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