I would like to use iCloud both for backup and syncing my iMac and MacBook Pro (as well as making files accessible to my IOS devices). If I move my files to iCloud (as opposed to copy and paste) then I obviously have a sync since they are in only one place. But I have slow internet and want them quickly accessible. Can I keep them in all three places (iMac, MacBook Pro, and iCloud) and keep them synced? And how do I establish the initial sync?