The first one is pretty cool for close combat users.... Again lol. Starting to see a trend

You usually coat your hand in a specific poison and do some sort of taijutsu strike that would cause a wound (scratch or using your finger to stab someone) that the poison can enter. Once the poison enters a wound of any sort, the target becomes paralyzed for two turns. Since my sword can be used as a source of the poison, I would combine this with a kenjutsu attack to cut someone and release the poison at once, paralyzing someone with a cut.
The second is basically a strong blast of gaseous poison that can physically harm with pure force but also comes with effects that worsen turn by turn. First turn the opponent can't make more than 4 hand seals and will worsen by 1 for each turn. Only thing I'm questioning is, is the -20 from tai something that happens during all turns or just the last?
The last one combines both gaseous poison and liquid. Creating 5 liquid blasts with gas inside of it (both same type of poison but different states of matter) I'd be able to attack people. On contact the liquid causes into pain and damage to the skin, while the gas inside explodes for the targets to inhale. The gas will cause 3 levels of speed reduction and the attack is equal to elements to to its dual nature. I'd use this with a target trapped/hidden in a closed space so the explosion has an even bigger chance of catching them in the gas.
Yeah the trend of poison working best in short range certainly is noticeable in the lower rank poison jutsu, as for your question the wording is ambiguous but I'm interpreting it as the -20 to taijutsu is present for the full duration of the poison, not just the last turn. That's how I'd check it if the issue ever arose I believe.
Alright next three, they are starting to get pretty interesting now.
( Doku Sōzō ) Poison Creation
Type: Supplementary
Rank: A
Range: Short - Mid
Chakra: 30
Damage: 60 ( rest depends on the copied poison )
Description: The user is able to take an existing sample of a given poison and manipulate it with his chakra, increasing the quantity, replicating it. Basically, much like one does with water release and a water source, the user is able to use a small sample of poison to, from it, create waves, projectiles, etc if the poison is liquid or a dust, clouds, gusts, mists, etc if the poison is a gas. This technique, however, cannot create poison out of nothing, only manipulate existing poison from a sample or source.
Note: The original sample or source needs to be within short-range of the user.
( Dokuton: Soeki no Jutsu ) - Poison Release: The Plague Technique
Rank: A
Type: Offensive
Range: Short
Chakra: 30
Damage: N/A ( 30 per turn if poisoned )
Description: A technique which is a very deadly poison skill which can subject even the strongest shinobi to extreme pain. By infusing highly concentrated poison chakra into one part of the person's body through direct contact, liquid poison begins to spread across and through the body causing purple dots to appear all over the body. As they spread, they constantly cause more pain as time goes on lasting for 3 turns. The effect is achieved by using the user's chakra to create poison inside the enemy's cells through direct contact and using only the normal toxins and byproducts of the enemy's metabolism as the source. The chakra will potentiate these toxins and multiply them, creating a cascading effect of increasing toxicity which can culminate in rendering the opponent unconscious if he doesn't stop the spreading of the technique or receive treatment in time.
Note: Can be used twice with a 4 turn cool down
( Ninpou: Dokugiri ) - Ninja Art: Poison Mist
Rank: A
Type: Offensive
Range: Short - Long
Chakra: 30
Damage: 60
Description: This version of Poison Mist is used by Ibuse, Hanzo's Salamander. When used by Ibuse, the salamander exhales a gaseous poison mist that when inhaled causes the target's body to go numb if its effects aren't countered. With the target paralyzed, the summoner can attack at their leisure. This poison will reduce an opponent's speed and reactions by 50% and reduce their taijutsu and kenjutsu damage by 20 rendering them more susceptible to attack.
Note: Usable only by Ibuse and only once every 3 turns
( Ninpou: Dokugiri ) - Ninja Art: Poison Mist
Rank: S
Type: Offensive
Range: Short - Long
Chakra: 40
Damage: 80 ( 40 per turn if poisoned )
Description: Chakra is kneaded within the body and then changed into special chemical substances which are then ejected through the mouth in the form of a massive gaseous poison cloud that can blanket an entire battlefield. When this substance comes in contact with the air outside the body, it instantly changes and is transformed into a mist of deadly gaseous poison. As this technique combines ninjutsu, chemistry, and medical knowledge, using it requires fine chakra control and advanced ability in medical ninjutsu. The poisoned individual will suffer 40 damage per turn for two turns if poisoned.
Note: Can only be used by those with Medical Training
If you don't have med or salamanders just ignore the techs.