Syncing strategies

I would like a suggestion how to define a syncing strategy that allows me to have all the devonthink databases in synhc with my NAS server, to be accessed by the MAC when I am at the office, and in synch with ICloud, to be accessed by the Iphone/iPAD when I am out of office.

Do I have to synch all the clients (MAC, Iphone/IPAD) with both the two locations (NAS via webdav, Icloud), or it would be better for example to define MAC synch with both locations and Iphone/IPAD with Icloud location only?

How can I be sure that NAS and Icloud are completely in synch?

Is the NAS server actually used by multiple devices/computers?