Answer 1:
They all have advantages of their own type, Explosive Lava is for Fire and earth users, as you may know, it has attributes of Earth and Fire, there is protection that causes Earth Faint and Fire Faint, take extra Damage from earth and fire, and Lava Spirits that have a chance to inflict burn( best for fighting world bosses rather than PvP), the passive skill gives you higher attack damage. Demon Sound is a mix for Thunder and Wind users, Demon Song: Phantom Wave inflicts blind, gives you higher dodge chance, and Demon Song: Song of Fantasia gives the enemy extra cooldown on a random skill, the passive skill has a chance to lower the enemies damage done(kind of like what earth would do). Hidden Silhouette's Passive skill is capture, it lowers the enemies dodge rate by (x)%, you have a chance to inflict capture every attack, not 100% chance to do it though, Silhouette Strance inflicts Stun on both the user and the target (user 2 turns target 3), it is said to lower 2% hp every turn, but when compared to Hellfire's burn, it does 6% for 3 turns, it may be a bug, who knows, it's third skill inflicts restriction on the target for (x) turns(you need a ninja emblem for Hidden Silhouette). Enraged Forest is a mix of Earth and Water, it's passive skill is nature power, you have a chance to gain (x)% hp and cp every time you use Earth or Water ninjutsu, Smothering Bind stun the target for (x) turns, it's third skill, I am not sure of the effect sorry, but it is called Matsuri. Hope this helps