Second form:
addAction(Actions.moveTo(posX, posY, 10)));
should move your actor to posX, posY for 10 seconds.
The first form will move the actor 1-step to x and y, and after that move the actor immediately to posX, posY. Actions.sequenceperforms these actions one by one, they do not change each other.
( ) act() ? , Actor , , , .