On my iMac, I have set the sync to every 1 minute. On both my iPad and iphone I have set sync to automatic.
Yesterday evening as it took about 3 hours to sync some 4000 items database (index only) to my iPad - I find wifi connection slows during the evenings - I left the iPad on all night (mains powered) to sync another database, some 12,000 items. This morning, I noticed that the sync progress on the iPad was at circa 23,000 items. (You have already explained the difference in files, etc).
Q1 -Would I be right in thinking that by leaving the sync on iPad and iphone on automatic, the sync process is continually running to check for and update any changes?
Q2 - And if so then would it be better to manual sync those databases I want to use on my iPad and iphone as I go, rather than have them sync all the time?
Q1 -Would I be right in thinking that by leaving the sync on iPad and iphone on automatic, the sync process is continually running to check for and update any changes?
No, sync is not continually running when on Automatic. It always runs on an interval of some kind, unless it’s set to Manual.
Also, note syncing DEVONthink To Go needs the mobile device to be open and our application frontmost on the initial import/sync. The Background App Refresh option is controlled entirely by iOS and only allows approximately a 30 second window, when it allows it to happen. This means we can’t control if, when, or how long it happens. Subsequent syncs are faster since there’s less data being transferred.
Q2 - And if so then would it be better to manual sync those databases I want to use on my iPad and iphone as I go, rather than have them sync all the time?
That is a matter of personal preference, though manually syncing does limit the amount of network traffic and overhead of intervallic or automatic sync choices.
When you leave your iOS device on during a sync this will ensure the sync will continue. If there are new items to sync, the next sync after the current, long sync run will pick them up. If you set the sync to automatic, this should be happening right after the initial sync run finishes.
That fully depends on your use case. After the initial sync is done subsequent syncs should be rather quick.