Yes, once you in the group, you only need to publish a single event that all members of the group can then decrypt and view. 

The largest event is actually the welcome/invite event because it has the whole tree/group state included in it. It doesn't start to become an issue until the group is ~150 (based on the max size of nostr events) but there are a few ways I've thought about to get around that so it's not that concerning. 

 I red you asked about max kind size, does the group state change each add/remove a member? or are there other cases?
Thanks 

 The group state does change with each add/remove but those are handled via commit messages that only make delta changes and don't require the full group state to be sent around.  

 Cool