Have been to all three, all worth visiting.
Spent two nights in Amiens, the cathedral and the floating vegetable gardens are unique. visit-amiens.com/accueil/…les_hortillonnages
From Amiens there are a few trains going to Rouen, in case you have got the time and the interest.
All trains are TER so no need to book in advance.
All of these are less than 2 hours from Lille by train, but you would have to change trains to get to Brugge or Ieper. You do not have to book in advance for these trains.