Despite unlocking the ability and loosening restrictions with cross faction play it is still confusing beyond what it should be to understand.
You can invite opposite faction to a party but only if you are battletag friends or realID friends, or if you are in a community/guild together. Same goes for inviting them to your guild.
Group finder auto creates a cross faction group without the need for all of that nonsense as well.
However you can not trade with an opposing member unless you go into an instance.
You can only speak in party / instance / raid / guild but if you aren’t grouped you can’t understand each other in say or yell chat anymore unless you both use an in-game consumable or happen to be of a certain shared races using specific language or know the language of the furbolgs.
Using multi seater mounts? Not with cross faction friends.
A hand full of raid and dungeons as well as raid and dungeon finder options are also off limits.
If you can think of anything else to add, I’m literally only putting this together after a friend/new player was asking but there is nothing that really explains all these restrictions unless you’ve read every patch note to come out.