Thank you all for the feedback. I have -not- tried Dropbox, that's to say, sync via Dropbox.
Checked my 6 years old never used 2GB Dropbox account and it still works.
(I have a 1TB OneDrive account, that came with Office 365. Actually, if I were to create one or more Outlook accounts, I would get 1TB per account, with a maximum of 5 accounts)
When using Dropbox I assume...that files need to be on the Dropbox server?
I have spent quite some time on this matter (synchronizing PC<>laptop) and will probably stick to the SyncBackPro/SyncBack Touch solution.
I have not come across a sync tools that does preserve the modified date stamp of folders.
In all cases, new folder dates are created. Not preserving the folder modified date stamp is 'unhandy'. It is the usual Windows (Explorer) behavior, I know but still...
With Opus I am used to having the folder modified date stamp preserved though.
Wonderful, really, but likely complicated to achieve as none of the sync tools offer that as an option.
Tried with 'sharing folders' - using Network and Sharing Centre-Advanced sharing settings - have laptop and PC autodiscover each other, etc.,
Both devices show up in Explorer tree under 'Network'.
It requires a lot of clicks though to share folders one by one (properties->sharing) on both laptop and desktop. Haven't found a way to share an entire drive/partition. That aside, that option seems to be more convenient in case of desktop pc. Usually a laptop has a kind of power saving plan. It shuts off, thus connection is lost.
Will use SyncBack Pro Touch.