(Suiton: Hahonryuu) - Water Style: Destruction Torrent
I would use this jutsu as a cover, first performing a small scale jutsu toward the target & then creating this spiraling torrent to cover the jutsu used, free form would also be used in the sense of creating the torrent & as it travels toward the target, with the free hand I could hurl projectiles through the spiral which could also be blocked by the opponent's vision - if the torrent is being blocked by a fire jutsu, projectiles would still be able to pass through, if an earth jutsu then maybe projectiles attached with explosive tags, weakening the structure of the earth due to both water & explosion.
Defending against this jutsu would require a large scale jutsu, due to the torrent moving in a spiraling motion. A wall of some sort would be the best idea if a rushed to defend against the water, projectiles could also be thrown through the gap between the torrent before defending against it.
(Suiton: Suiryuudan no Jutsu) - Water Style: Water Dragon Bullet Technique
As a basic strike out attack, the best time to use this would be at long range being able to take advantage of any spare time possible, once created it can be best used to simply attack the opponent head on which as said could cause major damage, or even have it attack from above by arching over as it travels. If holding a handseal is unnecessary after it is made then creating a distraction from underneath would aid in creating a successful opening for the dragon to collide. The safest way to avoid getting hit by this jutsu would be to avoid it rather than defend against it, the momentum & scale of the jutsu could easily break through most defensive structures within reason (Rank), using a hiding like a mole technique would be a good choice.
(Suiton: Suiryūben) - Water Style: Water Dragon Whip
Due to speed of the jutsu & the ability to maneuver the whip around, I would best use this having the whips arch around toward the opponent giving them less chance to defend or counter, if able to I would control a certain amount of whips to attack the opponent first & if they attempt to avoid the the whips I would send the remaining whips toward the target giving them a lesser chance to avoid. A wide scale Wind jutsu would be preferred in this situation, being able to scatter a large (if not all) amount of whips & depending on rank, still strong enough to carry on toward the opponent.