Ok. My wife just verified that she can access the GL-AR750S mount point and folders using Win10. Win10 File Manager prompted her to turn on Network Discovery, and she set it as a Private network.

When I was setting up with passwords, I could see the shares but not access them if I had anything in the “Allowed users” field Luci → Network Shares. I assume that your shares are showing up on that page. Settings there should be Browsable and Allow guests (read only if you want).

BTW for share/samba/usb changes, the router needs to be re-booted for them to take effect. There is no auto-mount when the usb is inserted.

With the default settings, my 750S gave access as specified in Luci with no need to change any configuration files using ssh. You might try reloading the firmware and going back to the defaults. I am now using the latest “testing” firmware without any problems, if you want to try that.