It syncs every 15 minutes, checking LionDesk for any new contacts, updates, and making sure Mailchimp is in lockstep

Yes, you can sync all your contacts and build a quick email newsletter list, you can also build additional syncs that send contacts to targeted lists based on any combination of criteria in LionDesk involving Contact’s Status, Source, Hotness, and Tags.

Yes, you will want to create correlating custom fields in Mailchimp before starting the sync, and then you will have total control and can map those custom fields to each other before starting this sync.