Ultra Smashes are can only be performed by Hitting the ''Y'' button on common controls when localed in the Ultra Smash circle
However , the Ultra Smash chance only appears when:
A) Opponent ''saves'' the ball , as in you hit the ball by throwing yourself in there just as is about to go away so you dont miss it. This is heavily punished in this game on Standard and Mega Battle mode as it will always result in US chance for the other player.
B) Opponent hits the ball with a ''weaker'' response.
If you happen to shot with a Fire Flower shot and the opponent DOES NOT HIT BACK WITH A CHARGED SHOT , it will result in a US chance for the other opponent.
C) As a Power type character , charging shots + Fire Flower chance always result in the opponent getting knocked away to the back of the court leaving a US chance.
I use the above trick sometimes , because its fun to do as Rosalina taking advantage of her strenght :3
In the end , charging the ball STILL affects the gameplay greatly , as well as alternationg between flat , top spins and slice shots.
Lobs are not as effective this time around , mostly on courts with high bounce priorities.
Additionally , even if you do happen to shot back a Ultra Smash from your opponent , if you hit the ball with the common buttons you will still give the opponent Yet another US Chance.
In my experience , to avoid this , if you recive a US , try hitting back with ''B+A'' which result is a slow shot , it wont cause yet another US chance.