Decision 01
Turn-based by default, live when possible
Live matches need everyone online at once, which rarely happens in a group of friends.
Considered
Live-only matches with a waiting lobby.
Chosen
Games start turn-based with a notification when it’s your turn, and switch to live play when both players are in the app.
Why it works
Friends can keep a game going through the day. The cost is more game states, which I made readable as a your turn and their turn list on home.