The two standout small forwards so far that are actually playing as small forwards are Isaac Kako (essendon NGA) and Joe Berry. You can also include Malakai Champion here.
There are a few that play high half forward more than your classic small forward role. Those guys generally also play a lot of midfield at this level but probably project as forwards at the next level. Guys like Taj Hotton, Murphy Reid.
Then there are the forward/mids that are bigger, more medium sized like Zak Johnson, Harvey Langford and Archer Day-Wicks.
Its not always super easy to say who will end up as a small forward at AFL level.
If you want to follow one kid in particular then the obvious choice would be Isaac Kako. He seems almost certain to be a small forward, perfect skill set and size for it.