The recommended approach is to have the client (or server) who creates the Doc populate it with initial data. All other clients should sync before editing.
Full discussion: Initial offline value of a shared document
As far as I know it’s not possible to selectively apply or broadcast some updates and not others. As soon as you skip an update, that Doc has a “hole” in it. No other updates will work as YJS will wait for the missing update, ensuring that updates are not applied out-of-order.