Dream and Fantasy are very well stabilised with the latest technology it's unlikely that anyone would notice a lot of movement.
Forward and aft, yes have slightly move movement, but it shouldn't affect anyone unless your in a storm, and your sensitive to the movement.
The higher you are the better , deck two is poor as your closer to the movement of the sea, in random short movements and closer to the engines, it has also enclosed. Science tells us the further you are away from impact the least you notice it.
Decks 7/8 would iron out the impact so not short random movements but a more gentle sway.
Also to help with motion sickness, you need to get fresh air, and view the horizon at the widest point, again decks 7/8 are far better than that.
Midship/ mid deck is the very best but to be honest the differences on these newer ships where they try to avoid bad weather or strong currents is negligible.