Any idea whether QR codes can be generated for each section, such as 'guides' or 'events,' or just one for the overall Facebook group?
You may generate a single QR code for your overall Facebook group or different QR codes for each section of your Facebook group. The QR code will always redirect you to the intended URL on scanning.
However, it depends on your Facebook group settings whether your group or its sections are visible on scanning the QR code if the group is private.