Do my friends and I have to select the same server to play custom lobbies?
Follow up for https://gaming.stackexchange.com/questions/398536/does-multiversus-progress-carry-on-between-servers-regions
In MultiVersus, the progress you have made in unlocking characters and perks doesn't reset when you select different servers to play online on.
If I want to play custom lobbies online with my Warner Bros friends, do we have to agree to select the same server to play on?
Yes, you have to be on the same server.
Worldwide there are different regions, and people usually choose the nearest one to minimize ping and lag. Matchmaking is created only with players on the same server.
Unless you have a sort of pre-lobby in game, where a friend invites you and other people to play together. In that case only the leader's setting will matter.