Walkthroughs for custom maps.

And for those familiar faces who are going to play together in the same room, I think custom PvP maps are much more suitable...

PvP maps, because the fixes have long since passed their stage of evolution. Dandy is absolutely right, studying the map is a boring and tedious process, which is why it's not popular. It's much more interesting to quickly play a game of Jebus. The only maps that are popular now are arenas, where the whole game boils down to one final battle.

As for cooperative mode, there isn't much point in it: constantly loading save files in multiplayer makes the game very uncomfortable.

Added 2 minutes later

You don't need to study the map in advance; ideally, it should be unknown to the participating players. Or play on the same map after a very long break, but again, without studying it beforehand.

This is almost impossible, because you need to draw a separate map for each game, which, of course, no one will do. And the beauty of playing on a fixed map lies in studying it and implementing some interesting plan/strategy (as in offline mode).