<Firstly, am I right that server broadcast calls are received by all client computers subscribed to it, regardless of which client computer initiates the call?>
<Does it queue those messages and send them all together on the next client download each time? (hopefully)>
Yes. If available, Errai will send multiple messages in a single transmission.
<Also, is there a way to set it so that each client only gets the latest message in that "queue"?>
No. The clients will receive all message that have been available during the transmission window.