Windows File History simply keeps copies of files in a special (IIRC, hidden) location. Whereas SE copies the files you point it at to where you tell it to. Not sure how they could conflict, as they're two separate processes. If you don't want the File History re-copied (and your Source in the SE profile points at or includes that location) simply de-select it using the Choose Subdirectories and Files functionality.
Unless you expect independent changes on the NAS or USB drive (to replicate back to the PC) SmartSync is not appropriate. You need either Backup or Mirror, depending whether you want to replicate deletions on the PC to the backup or not (where 'no' = Backup, 'yes' = Mirror).
Unless you expect independent changes on the NAS or USB drive (to replicate back to the PC) SmartSync is not appropriate. You need either Backup or Mirror, depending whether you want to replicate deletions on the PC to the backup or not (where 'no' = Backup, 'yes' = Mirror).