Using Publish in a AE

When using Publish in a AE the Peoplebooks say

Note:  If you’re publishing a message from within an Application Engine program, the message won’t actually be published until the calling program performs a Commit.

My question, is there a lock held on the pubid table until that commit is reached preventing other publishes from happening?

Does Deferred_Mode only really help in component transactions and not so much in a AE that is not using CI?

Is the best practice for a AE using publishes to commit after each publish or a controlled number say every 5 publishes?