Playlist is available in the binding, but album or category not. I would also go for 1 because otherwise you probably keep polling the data in the background, while it probably won’t change that much. (Having a playlist channel, might already be a bit of an overreach). I’ve not checked, but the spotify api has a lot of access rights options. The binding request only access to what it needs, so you might have access problems. If that is the case let me know and I’ll update the binding.
I don’t know if somebody has done it. There is a habpanel widget that was developed before the Spotify Binding was developed that uses a python script (openHAB integration to Spotify Web Connect API (player)). That widget could serve as a starting point (it should become simpler as parts of that widget are handled by the binding and no need to install python or configure the python script). I don’t know if someone has worked on it, it has been referred before but I’ve not seen an updated version.