Apparently it’s not needed anymore. There was a mod that recommended to enable full control for the windows shares:
but I found out it works even without, and I suggest you to disable full control for that share & user, otherwise the files could be modified/deleted on owncloud and you would lose them also from your HDD. I decided to give read-only authorization, which is the best choice in my opinion, so my files can’t be deleted.
You could share a particular folder (e.g. Public) with read/write permissions so you have a folder editable but your other shares are safe.
Also, don’t forget to enable encryption (masterkey; you find it in the server options) and generate SSL certificates: either on your own (but they will be flagged as unsafe) or from a provider, which you have to pay for or for free (eg https://letsencrypt.org/ ). We tend to forget it, but once you are “out in the open” there are threats and dangers. If you want to access your owncloud server from different clients on different networks, they’ll most likely get blocked as “untrusted domains”: add their IPs to your config.php trusted domains or add your public IP address to the trusted domains in the config.php to prevent the “untrusted domain” page to show up.