You would have to do both units 3/4 VCD since the folio is spread across both of them. If they haven't changed anything, the early design stages take place in the later part of unit 3 and everything starts to wrap up in unit 4. What you can make is quite broad since I believe you create the fake client, and is usually planned out with the help of your teacher who knows what would be feasible.
I remember going on a trip to the museum when they had an exhibition showcasing high quality VCD work (Top Designs?) and definitely remember seeing someone who created a deck of playing cards as one of their two presentations. I think the accompanying presentation was a caravan design - something along the lines of when going on a road trip or camping in a caravan, people often play card games. I believe the cards were designed around the idea of 'maps' - linking back to travelling and the caravan. From what I remember, the two presentations you make for your folio need to be in some way connected.
For things like packaging, cards, etc., which are more feasible to create prototypes/samples, I think the expectation is usually that you develop some sort of physical product nearing the end of the folio. With something like playing cards, you could potentially print them professionally after designing them to show them off as your final presentation. Obviously it isn't limited to things that are 'small' - I remember seeing plenty of fashion design works at the museum with wearable clothing on display.
I recommend getting in contact with some of your teachers who take unit 3/4 VCD to ask them what it involves and see if they can show you some past student's work.