How K-9 handles IMAP connections?

Could someone explain to me how K-9 handles IMAP connections? Am I right to think that for all folders, for which “push” notifications are configured there are separate active connections and for the remaining folders, which are set to be periodically checked there is one common IMAP connection initiated periodically?

How K-9 optimizes IMAP connections for mail servers with low limits of concurrent connections?

Yes, that’s basically how it works.

It doesn’t. What kind of optimization do you have in mind?

For example switching from IDLE to periodic syncing for some IMAP folders, when it notices connection limit has been reached.