I done my first TA in November last year on Explorer on 5th November I think it was. the first 2/3 were the worst we've ever experienced. granted we went through the bay of Biscay in November so that's never good. and our room was deck 6 at the front so heard the waves crashing against the hull which kept us up.
However on Day 4 everything was really calm.
we departed from Southampton but I've heard if you go from Barcelona it is a lot smoother as you a further south and miss the rougher seas.
I hope I didn't scare you, just my opinion of my TA