There are typically two types of jackfruit you can buy. 'Young' or 'ripe' (a lot of people refer to young as unripe, but it's actually not completely unripe, it's more 'underripe'). Young jackfruit is firmer and stringier which makes it ideal for 'faux-meat' recipes such as this pulled jackfruit. The colour of young jackfruit will also be green as opposed to yellow when it's ripe. The taste will also be less sweet the younger it is.
Most pulled jackfruit recipes use young fruit but I did actually make it with fresh ripe fruit as that was what I've been able to get the last few months. It is softer and sweeter but it's still a tasty combination. Most likely you'll find it easier to find canned young jackfruit than fresh anyway. Just don't buy the canned stuff in syrup as that is extra sweet!