I've deleted your 1st post/thread and kept your 2nd (they were more or less duplicates, but the 2nd actually has more detail).
No, the drive letter is as high as you can go in SE. You'll need two profiles, one each for C & D. Bear in mind that as per Help > Quick Start > Understanding Backup and Synchronization - and reprised here, SyncBackSE/Pro are not designed to (and can not) make an exact copy of a system drive.
You can back up OnChange or Periodically via
Modify profile > Expert mode > When > options
Note that SE has to be open in the background at all times for these options to work (that is, if you close SE they will stop until you restart it, and by default will warn you of that if you try to close it)
Bear in mind that OnChange will trigger if a change is detected (note also that it almost certainly won't detect changes on the NAS, as per the Help). But it will still scan afterwards (it won't blind-copy the change, but will scan for any other differences first, also 'which side should win'). It will also trigger on the creation/deletion of temp files (you can add Filters to stop such files being copied, but you cannot prevent them triggering a scan)
Actually, if you are not expecting independent changes on the NAS, SmartSync is not recommended anyway - suggest consider Backup or Mirror. If there should not be independent changes on the NAS (independent of your PC), then by definition any such changes are 'unexpected' and could be unwanted (e.g. files not being listed, which a SmartSync might interpret as having been deleted since last scan, and replicate that to your PC). If changes should only be happening on the PC, it would likely be wiser to use a profile that only copies data in one direction ('PC to NAS').
No, the drive letter is as high as you can go in SE. You'll need two profiles, one each for C & D. Bear in mind that as per Help > Quick Start > Understanding Backup and Synchronization - and reprised here, SyncBackSE/Pro are not designed to (and can not) make an exact copy of a system drive.
You can back up OnChange or Periodically via
Modify profile > Expert mode > When > options
Note that SE has to be open in the background at all times for these options to work (that is, if you close SE they will stop until you restart it, and by default will warn you of that if you try to close it)
Bear in mind that OnChange will trigger if a change is detected (note also that it almost certainly won't detect changes on the NAS, as per the Help). But it will still scan afterwards (it won't blind-copy the change, but will scan for any other differences first, also 'which side should win'). It will also trigger on the creation/deletion of temp files (you can add Filters to stop such files being copied, but you cannot prevent them triggering a scan)
Actually, if you are not expecting independent changes on the NAS, SmartSync is not recommended anyway - suggest consider Backup or Mirror. If there should not be independent changes on the NAS (independent of your PC), then by definition any such changes are 'unexpected' and could be unwanted (e.g. files not being listed, which a SmartSync might interpret as having been deleted since last scan, and replicate that to your PC). If changes should only be happening on the PC, it would likely be wiser to use a profile that only copies data in one direction ('PC to NAS').