I’d tend put something in to a category when possible. Trouble is we have a number of editors who follow Discogs rules where something has to actually be quote somewhere to allow “album” “EP” “Single” to be selected.
First I’d look at the artists own website. Second I’d look for some fan based website with a catalogue. Maybe I’d check Wikipedia.
Generally Albums are usually obvious. It is Single vs EP that gets a bit harder to predict.
I’ll also roll out the same old Single vs EP quote from Seal
The difference between an EP and a single is that a single has one good track and one throwaway track on it. An EP has three good tracks and is meant to be listened to as a whole.
The biggest guide I follow is - what are other editors of that specific artist doing? I’d aim to try and keep demos together instead of a split between nothing, album, EP, single… I like tidy.