Like the above post, I was in Belgium this past weekend when there was a strike, there will be trains on all routes, just a reduced schedule, and it is possible that specific trains will be "cancelled" on short notice. For example, the schedule showed the Intercity Direct train running from Antwerp to Amsterdam, but it was marked "Niet Ridjen" shortly before it was due to leave.
Since trains are all essentially regional transport, you buy a ticket for the route, and can take any train (except Eurostar) that is running on that route. The trip to Ghent is most likely a train to Brussels Midi, then change to a train to Ghent. There are a few trains that would require no change, but much more flexible and more options if you do change at Midi.